JOURNAL OF LATEX CLASS FILES, VOL. 18, NO. 9, SEPTEMBER 2020 1 Robust Lane Detection and Tracking based on Cascaded Feature Extraction and Inter-frame Similarity Saumya Srivastava1 , Rina Maiti1 , 1 Center for Product Design and Manufacturing, Indian Institute of Science, Bangalore, India ssaumya@iisc.ac.in., rmaiti@iisc.ac.in Abstract—Despite the development of several vision-based lane detection methods in past decades, lane detection is still a challenging issue in the computer vision community. The presence of shadows, obstacles, different symbols, and changing illumination conditions makes the task of detecting the road demanding. This paper proposes a robust framework for multilane (ego, right, and left) detection and tracking system. Two algorithms are proposed for extracting lane features, one takes into consideration the edge information of the image whereas another algorithm is based on extracting white and yellow lane marks using HSI color space transformation. Straight Hough lines and curved lines are plotted on the extracted lane mark using a first and second algorithm, respectively. Proposed work utilizes Inverse perspective mapping for the following three aspects: (1) Implementation of Noise elimination module in the pre-processing stage (2) detection of a pattern of broken lines (3) Curve fitting of the quadratic polynomial model using least square error for both, continuous and broken lane marks. (4) Execution of candidate line selection Module. Kalman filter is used for continuous tracking of lane line location and its corresponding lane parameters. Index Terms—Hough Transform, Lane Detection, Advance drive assistance system. I. I NTRODUCTION Multilane detection system plays a crucial role in many advanced driver assistance modules, such as It gives information about the ego lane as well as lane next to ego lanes. Which could be further used for Lane Departure Warning Systems (LDWS), Lane Keeping Assistance Systems (LKAS) using single lane detection, and Lane Changing assistance Systems (LCAS). Lane detection primarily consists of three stages: extracting lane features which are based on some visual clue, model fitting, and then tracking. In the presence of different sensing modalities in the market, such as lidar, radar, and GPS, the Vision modality, being low-cost and correlated to the human visual systems, is prominently used for gaining the perception of the vehicle’s surroundings. There are various sensing modalities used for road and lane understanding, including vision (i.e. one video camera), stereo, LIDAR, vehicle dynamics details procured from car odometry A Manuscript created October, 2024; This work was developed by the IEEE Publication Technology Department. This work is distributed under the LATEX Project Public License (LPPL) ( http://www.latex-project.org/ ) version 1.3. A copy of the LPPL, version 1.3, is included in the base LATEX documentation of all distributions of LATEX released 2003/12/01 or later. The opinions expressed here are entirely that of the author. No warranty is expressed or implied. User assumes all risk. or Inertial Measurement Unit (IMU) with global positioning information obtained GPS and digital maps. Vision is the most prominent research area in lane and road detection due to the fact that markings are made for human vision. Advance driver assistance systems which either alert drivers in a dangerous situation or take actives part in driving, are gradually being introduced into vehicles. So, there exists a bridge between the driver and their perception about the surrounding of the vehicle. The bottleneck to tackle the perception problem has two elements: road and lane perception, and obstacle (i.e., vehicles and pedestrian) detection. Road and lane understanding includes detecting the extent of the road, the number and position of lanes, merging, splitting, and ending lanes and roads, in urban, rural, and highway scenarios. Also, it is shown in papers that by including vehicle tracking, that lane tracking performance robustness, localization, and temporal response get improved. Multilane detection is the indispensable area when it comes to providing better perception of surroundings of the vehicle. However, these feature extractions using visual clues are susceptible to varying illumination, This paper is organized as follow: section 2 briefly reviews related works on lane detection system. Section 3 describes proposed lane detection system. Section 4 shows the details of the experimental work, results along with the limitation of the proposed method. Finally, section 5 concludes the paper with inclusion of future work. Lane detection comprises of three elements in its pipeline: feature extraction, model fitting and tracking [1]. With the intent to extract features, many studies explored the property of white and yellow colors associated with longitudinal lane marks [2], [3]. However, varying illumination and cast shadow on road surface due to trees, vehicles, building etc. provide hindrance in collating these color clues. To circumvent these conditions, studies have taken color-space transformations into consideration [4], [5], [6], [7], [8]. These color model disassociates the intensity constituent, the achromatic section, from the color carry information, constituting the chromatic section. Using the invariance property of lane color, different local or global techniques such as histogram-based segmentation [3],otsu thresholding [9] clustering method [8] adaptive thresholding [10], are exploited to detect lane marks. However, these methods are susceptible to conditions where during different illumination, road surface is also classified into lane markings. JOURNAL OF LATEX CLASS FILES, VOL. 18, NO. 9, SEPTEMBER 2020 Another well-known method to extract lane features are based on the image gradient or edges. Some studies [25], [22] have explored gradient properties by using oriented gaussian kernels, which prove effective for detecting bright lane marks against a dark background. However, these methods face challenges in situations with varying illumination and instances where noise, such as from certain parts of white cars, results in sharp gradients. Other studies employ detectors like Canny [11], [12] and Sobel detectors [13], known for their low computational cost and ability to yield valuable structural information about lane marks. Various improvements to canny edge detection has been introduced in the literature [14], [15] to effectively address noises in the road environment. Wu et al. [16] extracted lane mark edges by using predefined local edge orientation range and multi-adaptive thresholding algorithm on sub image level. In [13], Kang et al. proposed a combination of local line extractor and connected component algorithm to extract candidate lines of road lanes in the sub-region. Another method for enhancing lane feature is presented in the work by Yuan et al. [17], wherein modified local adaptive threshold is applied to segment road pavement. Additionally,a denoising operation with constraints on both area and orientation, is applied to refine the results. Li et al. [18] utilized HSV color transformation to extract white lane marks, followed by edge detection of binarized image in ROI area. For all these methods, noise removal is post requisite step after edge detection. However, challenges arise during noise eliminating such as (1) presence of misleading edges originating from artifacts such as strong,aligned shadows of trees, buildings, or other infrastructure, road marking patterns, cracks, and stains. These elements exhibit a similar orientation to lane mark edges, resulting in the failure of accurate lane edge extraction.(2) risk of inadvertently wiping out small edges corresponding to broken lane marks in the course of noise removal. (3) instances where lane edges are embedded with clutter. In attempt to remove noise, valuable information is often unintentionally erased and alters the structural information of the lane edges. This exerts a significant impact on the overall effectiveness of subsequent processes. Numerous studies have been presented on the lane detection through the application of inverse perspective mapping [26], [28], [29].This geometrical transformation aims to eliminate perspective effects by homogeneously remapping picture elements to a new reference frame, thereby providing a top-down view of the road scene in front of the camera. Consequently, this process restores parallelization between lane markings, facilitating the determination of road deflection. Combination of ridge features and IPM has been used [30]. Though the method is independent of camera calibration and can withstand changing pitch angle but fails in handling roads with varying curvature. In [31], Jiang et al. proposed a method where initially central lane is detected by using perspective transformation. However, method fails did not count for the scenarios where visual clue of central lane are absent. In [32], proposed method uses conditional random fields that works well for both, parallel and non-parallel lanes situation. However, performance of the method degrades in the anomaly of normal weather condition or in the presence of leading vehicle which occludes lane markings. Zhaom et al. [33] needs additional information such as lane width, vehicle speed and direction in order to design a model. This additional 2 information requires higher costs. These approaches works well under the assumption of flat road;however transformation is vulnerable to vehicle vibrations. Additionally, the leading vehicle can obstruct the lane mark, causing artifacts in the IPM transformation. II. R ELATED W ORK Here, we discuss several existing methodologies aimed at exploiting inter-frames similarity technique, highlighting their effectiveness but also acknowledging their limitations in accurately detecting lanes across diverse environmental conditions. A. Conventional tracking methods In the domain of lane detection,tracking is often used to deal with scenarios where lane markings are difficult to detect. [35], [43], [27]. In [16], Wu et al. used kalman tracker to track end coordinates of the lane marks. Other approaches involve the use of hough transform-derived parameters, such as ρ and θ, to define the state vector for the kalman filter [28], [42]. However, kalman filter performs optimally only when the underlying noise follows a gaussian distribution. B. AROI, LBROI In line with the concept of inter-frame similarity,numerous studies define a region of interest (ROI) around the detected lane markings.This ROI serves as a predictive space where lane markings are expected to be located in the subsequent frame. By constraining the search area, not only does it eliminates background noise, but also reduces computational overhead. Jung et al.[19] proposed the lane boundary region of interest (LBROI), to search edge information about lane boundaries in the next frame. Similarly, Yuan et al. [17] introduced the adaptive region of interest (AROI),which dynamically adjusts its size and position based on variations in lane curvature and vehicle speed. While the method is effective in scenarios like lane changes by re-identifying the starting point of the lane for every 20th frame, it falls short in cases where consecutive frames following the 20th frame produce false positive or negative detection outcomes. This limitation has the potential to propagate false AROIs until the next re-identification process is executed. C. Λ-ROI In Lee et al. [40] work, apart from establishing Λ-ROI , interframe clustering is also employed, where aggregated statistical information about slopes,lower intersection locations, vanishing points and lane widths are clustered over a designated frame sequence. The aggregated data is then tracked through the use of a kalman filter, which plays a crucial role in handling missing lane markings. Their methodology works well if noise is inconsistently present over frames. Λ-ROI with distorted trapezoid shape and variable boundaries ensures continued detection of lane markings despite changes in lane width or vehicle shifts horizontal beyond the typical range. For detection part, their methodology used scan-line test that is based on low-high-low intensity profile of lane markings and their derivatives.However, line segments from other vehicles, shadows, or buildings may survive the slope filtering and the clustering if they are parallel to the lane markings. JOURNAL OF LATEX CLASS FILES, VOL. 18, NO. 9, SEPTEMBER 2020 D. left and the right lanes are tracked dependently In the study by [41], a spatiotemporal image is constructed by integrating pixel intensities along a scanline across the temporal axis. Their methodology relies on the presumption of temporal continuity in lane width. When one of the lanes (left or right) is absent while the other remains intact, the method leverages the temporal continuity of lane width for detection. However, in scenarios where both left and right lanes are fully obscured by obstacles, detection becomes unattainable. E. similarity for location consistency and estimated vanishing points Yoo [34] utilized inter-frame similarity for location consistency and estimated vanishing points, introducing a probabilistic voting function based on a line segment strength parameter that quantifies the relevance of extracted line segments. All these approaches relies on the assumption of a consistent presence of lane markings at similar locations across consecutive frames. However, real-world driving scenarios often involve non-linear events such as sudden change of ego lane and the introduction new lane marks or discontinuation of existing lane marks (e.g., parking marks). While highway lanes typically maintain constant widths, urban roads often see fluctuations in lane marking locations and widths, particularly around road junctions.These dynamic driving conditions pose challenges to the validity of the inter-frame similarity assumption, as they lead to changes in parameters such as lane width, slope, and position of the ego lane over time.**3) accuracy of tracking in end depends upon accuracy if detection. If the dynamic of road changes, then motion model also goes obselete. motion model, lane -width, ROI Didnot address the validity of new detection latency is involve, which can be overcome if more sensor information are fused together. THOUGHT** For a established ROI, no lane marking is detected, kalman will take it as a missing detection and predict the lane marking.However, a different lane marking exist beyond the ROI, therefore false positive will arrive.Similarly, with no lane marking detected, for the next frame width of the ROI will increase and detect a lane-like noise over persistent frame and take it new lane marking.What happened to the results obtained from kalman filter.!!! no proper reasoning/ explanation is given; open ended;Discussion needs to be done; conflict arises;ambuigity In the proposed work, two modules are proposed. First one deals with detection and second deals with inter-frame similarity. For the detection of l,both local statistical and geometrical properties of lane marking are exploited using two stage feature extraction. The first stage involves adaptive selection of candidate threshold values on a sub-image level, considering the geometrical constraint of pixel-width on longitudinal lane marks.Threshold value is validated using contrast offset and peak offset,with various margin values used to update final threshold. However, erratic patches apart from longitudinal lane marks with pixel value above threshold can surpass stage 1st . To eliminate such noise, denoising operation is performed in the second stage. Using vertical aggregation technique,peaks are selected to define window between two valleys. Subsequently, 3 thresholding is performed on the window level and hough transform is applied to select only aligned pixels. Straight line, implemented with RANSAC is applied for curve fitting in cases of both solid and broken lines. Once the detection is made, inter-frame similarity module is introduced. For each frame in a single span, deviation factor is calculated by comparing the detection with previous estimated output of the kalman filter. If the deviation factor falls within the tolerable pixel shift (TPS), the kalman filter incorporates the detection to estimate the output in the current frame; otherwise, it disregards the detection and uses prediction for the current frame estimation. A dynamic area of interest is established to search for the lane in the next frame. However, to address scenarios such as lane change,introduction of new lane marks, full frame detection mode is applied after every 10th frame.Verification protocols are followed , where if new detection is incompatible with results from the previous DAOI, a flag is raised, prompting the system to switch to fullframe detection mode for the next frame. Flag is raised till the detection result from full-frame becomes stable and DAOI is re-established with re-initialization of kalman filter. This work presents three primary contributions:(1) presents the detailed insights into solution for the challenges of lane detection in the real world scenarios like illumination variation, noises, vehicle occlusion, lane change and introduction of new lane marks (2) based on both local statistical and geometrical properties of lane marking, our method iteratively prunes the lane mark features,on both,sub-image level and window level by using two stage feature extraction level. (3) In addition, significant attention is paid to remove the noise signals from the background. (4) This work establishes successful co-existence by integrating detection with tracking and establishment of DAOI. III. P ROPOSED M ETHOD In the proposed work, we deal with two modules: 1) Lane detection comprising feature extraction and curve fitting 2)Interframe similarity involving DAOI establishment and the tracking system. It begins with extracting the individual frames from the video and transforming each frame to inverse perspective mapping to detect lane markers. To get the transform, it is imperative to have the intrinsic (camera optics, skew factor) and extrinsic (position, orientation) parameters of the camera sensor which deals with camera orientation, location optics and tilt. These matrices establish the relationship between camera coordinate and image coordinate. Longitudinal lane marks typically present as lines with yellow or white tint, appearing in continuous or dashed patterns, offering high visibility and contrast against the road surface. To extract this distinctive feature, the RGB color values initially undergo conversion into the HSV color space. This transformation not only aligns better with human vision but also facilitates the separation of chromatic components (hue and saturation) from achromatic intensity, enhancing the precision of feature extraction. A. Lane Detection Despite the restoration of lane marking parallelism, challenges still persist in the feature extraction process. These challenges include 1) instances of occlusion of lane marking by JOURNAL OF LATEX CLASS FILES, VOL. 18, NO. 9, SEPTEMBER 2020 Fig. 1. Challenges associated with lane mark feature extraction after IPM transformation. First row displays the original image for reference. (a) ∼ (c)artifacts arise due to leading vehicle and (d), saturation of image scene due to intense ambient light, (d) ∼ (e)presence of severe shadow. vehicles leading to artifacts in the IPM as depicted in Fig. 1(a), (b). 2) Risk of misclassifiying objects as lane mark candidates due to similarities in intensity and alignment, allowing them to pass through thresholding process. As illustrated in Fig. 1(c), the edges of the car exhibit similar orientation to that of the lane marking. 3) The varying illumination across the road scene. For instance, intense glare induced by background light or shadow cast by trees, can alter the dark-bright-dark pattern of lane markings against the road surface as shown in Fig. 1(d) and Fig. 1(e), (f) respectively. To address these challenges, both local statistical and geometrical properties of lane marking are exploited in our work. Based on the skewness of histogram, images in our proposed work methodology is classified as dark or bright image. Furthermore, each IPM image is partitioned into left half section and right half section using the central demarcation line at xm as shown in Fig. 2(a) . Two stage feature extraction is employed wherein first stage threshold values are adaptively selected on sub-image level and in the second stage denoising operation is performed on window level. 1) Adaptive Local Thresholding: To begin with, both section of image is initially divided into sub-image is of size r ∗ c such that r = 2c and for each sub-image, a histogram is constructed for pixel range varies from [0, (L − 1)]. Since, the longitudinal lane markings have distinguished property of being constant in pixel width taken as w, cumulative distributive function of the sub-image is then obtained such that cumulation satisfies the following constraint: ( 0 !) 0 X X b∗w∗r cdf(X) = P (X) | P (X) ≤ (1) L−1 k=L−1 k=L−1 where P(X) is probability density function which is defined as P (Xk ) = nk /N , L is the total number of gray levels in the image, N = r ∗ c is total number of pixels and nk is the cardinality at gray level k. The underlying assumption is that the lane marking consistently exhibits a brighter contrast compared to the road surface and typically occupies the right extrema of the histogram. The pixel index at which the cumulation stops as per the above-mentioned criteria is identified. Subsequently, to increase adaptability to diverse conditions, a margin, denoted as m1 and typically set to 20, is subtracted from the obtained pixel index. The resulting value is defined as candidate threshold index, th′ . It is validated only if it satisfies the following two 4 Fig. 2. Adaptive Local thresholding is performed over an image (a) sub-image is chosen from left half section of IPM. The central demarcation line at xm is depicted in orange (b) zoomed-in representation of sub-image (c) generated histogram of the sub-image (d) zoomed-in image shows contrast offset and peak offset (e) Accumulated pixels with red peaks beyond the candidate threshold th′ from(d) are highlighted, where sk′ represents the average cardinality for pixel intensities ranging from [th′ , L − 1] (f) sub-image obtained after performing Adaptive Local Thresholding (g) final image conditions: 1) contrast offset should be greater than τ1 and 2) peak offset greater than τ2 , where : Contrast offset = max (k ′ ) − arg max (nk ) (2) Peak offset = max (nk ) − sk′ (3) k where sk′ is the average cardinality for pixel intensity ranging from [th′ , L − 1] L sk′ = X 1 nk ′ th − L ′ (4) k=th and k ∈ [1, L − 1], k ′ ∈ [th′ , L − 1]. For a selected candidate threshold value, high value of contrast offset signifies higher contrast between foreground (lane marking) and background (road surface). Similarly, high peak offset validates the presence longitudinal lane marking with area w ∗ r embedded within a sub-image of area r*c. Pixels surpassing the validated threshold value are retained, while those falling below are assigned to value 0. However, absence of a distinct peak and a flat histogram indicate minimal contrast for a given sub-image. Consequently, all pixels within such a sub-image are considered as background and are assigned a value of 0. The outcome of local thresholding with parameters b = 1/7, w = 7, τ1 = 30 and τ2 = 10 is illustrated in Fig 2. 2) Window Denoising: It is evident from Fig. 3(c) that due to varying illumination across the image, the application of adaptive local thresholding yields an image with erratic patches along with white longitudinal lane markings .To address this, denoising operation is executed on window-level. To define window, histogram detailing the vertical aggregation of pixels is initially generated over resultant image. Under the assumption that lane marks maintain a minimum separation of at least 40 pixels, significant peaks are identified, as shown in Fig.3 (d). Subsequently, valleys located between these peaks are identified to define windows across the image, thereby signifying the presence of lane markings within each specified window. As can be seen in Fig. 3(e), two windows are designated across the rightside of IPM using vertical pixel aggregation.For each window, the pixel with the highest intensity is selected and updated by JOURNAL OF LATEX CLASS FILES, VOL. 18, NO. 9, SEPTEMBER 2020 5 have used tracking techniques. Kalman filter works well under the assumption of gaussian noise. It predicts well for the spurious detection. However, for the sudden change in the driving maneuver, kalman filter will consider new location as noise and doesn’t take it into account. In our proposed work two kalman filters are used to track the detected lane in the subsequent frames, one for left lane marking and other for right lane marking. It consist of two stages, first stage predicts the present state of the target as per equation described below: Fig. 3. (a) Original image (b) Right half section of IPM (c) Image obtained after applying adaptive local thresholding.The resultant image has erratic patches along with lane marks (d) vertical pixel aggregation over the image (e) Hough lines drawn on each window. subtracting the margin m2 and subsequently identified as the threshold. However, in the case of classified dark image with reduced ambient light such as those captured in cloudy, dawn and night scenes,has noise with intensity higher than that of longitudinal marking. These noises readily bypass the adaptive local thresholding in the preceding stage and results into sharp trailing lines. To address such scenarios, threshold is determined by selecting the index of arg maxk (nk ) with subtracted margin, m3 . Hough lines are then laid over the resultant window which not only removes further noise from the image, but also chooses the aligned non-zero-pixels. Moreover, dilation is applied to add pixels to object boundaries which helps in highlighting the lane features.The images displayed in the first and second rows of Fig. 4 represent the original and resultant IPM images, respectively. The third row illustrates the image post-adaptive local thresholding, while the fourth row displays the denoised output image obtained with parameters m2 = 40 and m3 = 5. Lane marks corresponding to ego lane is defined by farthest peak and nearest peak in left half section and right half section of image respectively. Second order polynomial function with RANSAC is used for plotting curve in case of both, solid and broken lines over each window. B. Inter-frame Similarity Inter-frame similarity in terms of temporal and spatial continuity is a widely employed concept in various research endeavors. In [17], Yuan et al. defined adaptive region of interest (AROI),wherein the position of lane marks in the previous frame are used to predict their location in the subsequent frame. While the method is effective in scenarios like lane changes by reidentifying the starting point of the lane for every 20th frame, it falls short in cases where detection result in false positives or negatives in the 21st frame. This limitation has the potential to propagate false AROIs until the next re-identification process is executed. We make our system robust by utilizing the inter-frame consistency in two aspects 1) for tracking lane mark and 2) for defining the Dynamic Area of Interest (DAOI). 1) Tracking: Lane markings play a pivotal role in our methodology; however, factors such as occlusion by leading vehicles, degradation due to wear and tear, pronounced shadowing, noise, and fluctuating illumination conditions can hinder their availability for extraction in every frame. To increase robustness of the system, numerous studies in the literature + û− t−1 = A × ût−2 + W (5) where ut is a vector containing the state , which in our case are the parameter of lane. Measurement vector Z at any time t for left and right lane marking consist of quadratic parameters : Zl = [ α0 , α1 , α2 ]l (6) Zr = [ α0 , α1 , α2 ]r (7) While initialization, velocity component are set to zero and A is a process transition matrix which establishes the relation between previous and current state in dt time difference. It then advances to estimate error covariance Pt− − Pt−1 = A × Pt−1 × At + Q (8) − Where Pt−1 is a priori estimate error covariance and Q is the process noise (white noise). Second stage plays role in correction of the predicted state using the measurement. Kalman gain K is computed to correct the estimated state as: − − Kt−1 = Pt−1 × (Pt−1 + Rt−1 ) −1 − − û+ t−1 = ût−1 + Kt−1 (zt−1 − H ût−1 ) (9) (10) It concludes the tracking stage by updating the error covariance Pt− to Pt : − Pt−1 = (I − Kt−1 ) × Pt−1 (11) where Pt is a posteriori estimate error covariance.Left and right lane parameters are calculated from kalman state space equation as: Fig. 4. Row 1 depicts the original image, Row 2 demonstrates the Inverse Perspective Mapping (IPM), Row 3 showcases the result post-application of adaptive local thresholding on a sub-image level, and Row 4 exhibits the final output after window denoising JOURNAL OF LATEX CLASS FILES, VOL. 18, NO. 9, SEPTEMBER 2020 6 i h + + + α c0 t−1 , α c1 t−1 , α c2 t−1 = û+ t−1 [1 : 3] (12) i h + + + α c0 t−1 , α c1 t−1 , α c2 t−1 = û+ t−1 [1 : 3] (13) r l By using the estimated parameters of the kalman filter, bottom and top x-coordinate of the fitted curve for left and right is estimated as follows: 1 + C + l x̂t−1 , l x̂t−1 = o n + + + c0 t−1 , α c1 t−1 , α c2 t−1 , yϵ1, C (14) x y = fl x, α 1 + C + r x̂t−1 , r x̂t−1 = o n + + + (15) c0 t−1 , α c1 t−1 , α c2 t−1 , yϵ1, C x y = fr x, α Deviation factor (DF) for both the left and right lane marking is estimated by subtracting the detected x-coordinate of the bottom-most and top-most point of the lane marking at time t from its previous estimated value at time t − 1 as DF l = 1 C 1 + C + l xt , l xt ) − (l x̂t−1 , l x̂t−1 (16) DF r = 1 C 1 + C + r xt , r xt ) − (r x̂t−1 , r x̂t−1 (17) To validate detection at time t, the deviation factor must fall below the Tolerable Pixel Shift (TPS), which in our case is taken a value of 15. TPS refers to the permissible deviation in pixel positions between consecutive frames within a video sequence. The Kalman filter incorporates measurements when the deviation factor remains within this threshold. A high deviation factor indicates increased detection error and measurement noise, prompting the Kalman filter to rely more on the existing motion model than the measurement. In such case, for the parameters α0 , α1 , α2 , the corresponding diagonal values of R should be large. r1 = r2 = r3 = 10025 2) Dynamic Area of Interest: It is a demarcated area with boundary x ∈ [xmin : xmax ] and y ∈ [1 : length(IP M )] around the detected lane marking in the nth frame which will act as potential lane marking search area for the next th (n + 1) f rame where xmin = x̂+ t−1 − wd (18) xmax = x̂+ t−1 + wd (19) where wd = 20 is pixel width used to define DAOI. Not only this reduces the processing time by limiting the scanning image area for the next frame, but also improves the accuracy of the proposed method by avoiding the noise in the entire scene. Adaptive thresholding method with subsequent application of hough lines and curve fitting as explained above is then applied to DAOI and lane features are retrieved along with quadratic parameters. 3) Integration of Detection, Tracking and DAOI: However, DAOI relies on inter-frame consistency that says lane does-not change substantially between two frames, proving inadequate to handle scenarios where new lane markings emerge abruptly in the road scene,such as parking lane marks appears for some frame and then discontinues in Aly’s dataset, cordova1 and cordova2 [25]. To overcome this limitation, entire image is scanned for both right and left half section for every 10th frame. Within span of 10 frames, detection result at time t is compared with estimated result from t − 1 to calculate deviation factor. Two distinct cases arises in such situation: 1) DF < T P C: detection over entire image is compatible with previous frame results and DAOI is established for the next t + 1 frame (2) DF > T P C: detection is incompatible with results from DAOI, kalman filter disregards the detection results and uses prediction for the current frame estimation. Full-frame detection mode is applied at intervals of every 10th frame in the video sequence. Flag is raised to makes the system go detection in full-frame detection mode for the next frame. If the detection 11th frame is incompatible with results from the previous DAOI, a flag is raised, prompting the system to switch to full-frame detection mode for the next frame. Flag is raised till the detection result from full-frame becomes stable and DAOI is re-established with re-initialization of kalman filter. To overcome this limitation,similarity span of n famres are slected , over which DAOI C. Lane Change In the real life scenario, lane change is frequent driving maneuver.To address such scenarios, For change in the lane to left side of the ego-lane: 1 + C + 1 C l x̂t−1 , l x̂t−1 → r xt , r xt (20) For change in the lane to left side of the ego-lane: 1 + C + 1 C r x̂t−1 , r x̂t−1 → l xt , l xt (21) XXXXXXXXXXXXXXXXXXX Once the lane change is confirmed, kalman filter is reinitialized for both left and right side of image. For the next frame, new demarcation, x′m is defined to partition the image into left and right halves.If lane changes to rightwards,new demarcation is defined as** It divides the images more from right side x′m = 1l x̂+ t + lw (22) It shifts the midline to the right of centre such that both the left and right lane marking detections are positioned on their respective sides relative to the new demarcation . Similarly, if lane changes to leftwards,new demarcation is defined as x′m = 1r x̂+ t − lw (23) where lw denotes pixel space between left and right lane marking .With empirical estimation, space pf minimum 30 pixels are chosen to define lane-width. Subsequently, a lane change flag is triggered, and x′m is utilized until both the left and right lane marking detections are positioned on their respective sides relative to the previous midline demarcation, xm . JOURNAL OF LATEX CLASS FILES, VOL. 18, NO. 9, SEPTEMBER 2020 7 Fig. 7. Experimental set-up forward movement of traffic and indicates vehicle’s position with respect to the road. These marking exhibits various colors and pattern. While solid yellow or white lane markings are relatively easy to detect, identifying them in worn or damaged condition present significant challenges. Moreover, other markings can act as source of noise that must be mitigated to ensure accurate detection of lane markings. Our proposed method is evaluated on two datasets:1) Our dataset 2) Caltech dataset. Our dataset and annotation is available on ref https://drive.google.com/drive/folders/11LcEWYz9HNufgEz1bHgvc0jtTm4 To capture the dataset, camera is mounted over the top of the vehicle and stabilized with the help of gimbal and rigs, as illustrated in Fig. 7. The recording occurs at frame rate of 30 fps on Indian roads. The experiments are conducted on PC equipped with 3.20 GHz Intel Core i5 CPU and 8 GB RAM. Images are scale to size 640 ∗ 340 and bonnet area is removed before IPM transformation. To verify the detection results, our evaluation methodology aligns with criteria proposed in Aly’s and Yoo’s work [34], [25], wherein detected line within every frame is compared to the hand labelled ground truth. To determine whether two are the same,distance is computed between N samples on detected line {l1 , l2 , l3 ...lN } and their corresponding nearest N sample on ′ ground truth {g1′ , g2′ , g3′ , . . . gN }, as shown in Fig.8. Mean and median are derived as: L L L d¯L = mean d1 L (24) G , d2 G , d3 G . . . .dN G L L L d˜L = median d1 L (25) G , d2 G , d3 G . . . .dN G Fig. 5. (a) lane change Fig. 6. (a)The orange line represents the mid-line, which divides the image into left and right sides. The green portion depicts the ego-lane for the driving car. The transition of the ego-lane from time stamp t − 1 to t occurs as follows: 1 b+ before the transition,1l x b+ t−1 < xm and r x t−1 > xm and indicating a leftward position of the lane; once the lane shifts to the right side, 1l x b+ t−1 > xm and + 1x b > x m r t−1 IV. D ISCUSSION On paved roads, markings over road provide direction for separating the traffic flow in the same or opposite direction and assistance to pedestrian and drivers. Road marking comes in various types such as longitudinal, transverse, hazard, block, arrow, directional and facility marking. Our proposed work focuses on detection of longitudinal markings,that ensures the Similarly, d¯G and d˜G is derived by computing the distance between N samples on ground truth {g1 , g2 , g3 ...gN } and their corresponding nearest samples on ground truth ′ }. For both detection and ground truth to con{l1′ , l2′ , l3′ , . . . lN cide, the following conditions have to be satisfied, min d¯L , d¯G ≤ t1 min d˜L , d˜G ≤ t2 (26) (27) 1) Our Dataset: Our dataset consist of 6427 images, recorded under varying illumination condition that includes cloudy weather, dusk, saturated ambient light and shadows. Clip1 was recorded on cloudy day with minimal traffic on the highway. There is enough contrast of black-white-black pattern on road surface and lane markings are clearly visible. However, clip2 and clip3 consist of traffic scenarios where location of JOURNAL OF LATEX CLASS FILES, VOL. 18, NO. 9, SEPTEMBER 2020 8 lane marking is not prevalent due to presence of pedestrian vehicle. To gauge the robustness of our proposed method, we conducted a comparative analysis on our dataset against three existing methods i.e, Aly [25], Xu[21], and Yoo [34]. Fig. ?? shows chart that proposed model surpasses the performance of existing models in terms of detection accuracy, estimated our dataset using t1 = 10 and t2 = 15. For our work, detection rate is calculated as follows: R% = Cr + Cl 2T (28) where T is total number of frames and Cl and Cr represent the counts of accurately detected left and right lanes, respectively. As shown in the first column of Table I, the work by Xu [21] yields very low detection rate. The methodology in Xu’s work involves employing 95% of the maximum pixel values as the threshold. However, single threshold is insufficient to handle the varying illumination levels across our different video clips. To address this limitation, we modified the method by empirically selecting the threshold tailored to individual clips. While it has improved detection rate in clip1, clip2, clip3, clip4, clip8, but the overall performance remains unsatisfactory, as evidenced by the results in the second column of Table II for clip5, clip6, clip7, and clip8. There are several issues associated with the work proposed by Xu [21]. First, lane marks gets easily removed by global thresholding, if saturation over one portion has dominance over lane marking features. Additionally, formation of ROI is susceptible to edges originating from vehicles, stains, or aligned noise. Such noises have the potential to form significant peaks during vertical aggregation and eventually form the strong connected components, thereby reducing the accuracy of the work. Aly’s method explored gradient properties by using oriented gaussian kernels, which prove effective for detecting bright lane markings against a dark background, particularly on new roads,as evidenced by detection results of 96.66%, 95.11%, and 91.28% for clip1, clip6, and clip8 respectively. 2D kernels, configured with specific width are used to produce filtered image.These filters are expected to produce high response to lane markings. Once the filtered image is obtained,pixel values above 97.5% quantile value are retained. However, with varying lighting condition and noise (other markings,IPM artifacts etc.), their methodology are prone to produce high false positive.In the absence of temporal integration, their methodology proved inadequate in scenarios where lane markings were obscured by leading vehicles, as evidenced by the detection results of 71.25%, and 70.57% for in clip2 and clip3 respectively. However, method is ineffective in handling noises with similar orientation that is in proximity to lane markings. Yoo’s method demonstrates superior performance when compared to other approaches. However, detection performance suffers in scenarios characterized by intense shadows, evidenced by a detection rate of 35% in clip6. To make the system robust, inter-frame similarity is used for vanishing point and lane angle estimation. However, the method does not effectively handle rapid changes in road dynamics, particularly during lane transitions, where angle constraints on host lanes may fail. This limitation becomes apparent with a low detection rate of 35% and 56% in clip6 and clip7, respectively, both of which involve lane changes. Additionally, a lower detection rate, notably in clip2, clip3, and clip5, is due to the presence of line segments collected from vehicles near the lane marks with orientations similar to those of the lane marks. This similarity disrupts the geometric relationships between line segments and the estimated vanishing point. However, method is prone to false detection in the presence of street writing, crosswalks, stop lines on cross streets. In such scenarios, filters design to detect vertical bright lines of a particular width may erroneously identify these symbols as lane lines. As can be seen in Table I, our work is presented in two modes:Mode1 entails the application of our method in a fullframe detection mode, while Mode2 integrates inter-frame similarity module with detection, where DAOI is established and tracking is applied. The proposed method outperforms other approaches with the average detection rate of 99.38%. In traffic scenarios where lane markings are occluded by leading vehicles, our method achieves a detection rate of 87.33% and 87.71% for clip2 and clip3, respectively, without the inter-frame similarity module. Similarly, low detection rate of 83% is seen for clip6, that deals with intense shadow and lane change scenarios. However, upon integrating the inter-frame similarity module, significant improvement over detection rate by 12.47%, 12.15%, 15.22% is observed for clip2, clip3, and clip6, respectively. Our method works well to maintain the definition of ego lane, TABLE I C OMPARISON OF L ANE D ETECTION R ATE ON OUR DATASET Clips Xu’s [21] Modified Aly’s Yoo’s[34] Our Method : Our Method: Xu’s [21] [25] Mode1 Mode2 Clip1 47.68 87.84 96.66 96.75 97.1 99.67 Fig. 8. Validation criteria. The distance is calculated by determining the Euclidean distance between N sampled points on the detection line (in red) and their corresponding nearest points sampled on the ground truth (in green). Clip2 54.15 75.71 71.25 89.08 87.33 99.80 Clip3 49.71 74.57 70.57 91.71 87.71 99.86 Clip4 3.61 81.12 89.74 99.01 98.86 99.28 Clip5 54.35 59.46 85.91 38.68 98.85 99.01 Clip6 55.24 59.54 95.11 35.78 83.11 98.33 Clip7 49.43 52.71 84.00 56.29 92.42 99.14 Clip8 11.29 58.71 91.28 98.00 91.28 99.85 JOURNAL OF LATEX CLASS FILES, VOL. 18, NO. 9, SEPTEMBER 2020 9 Fig. 9. Lane detection results on our dataset samples: Row 1 - Aly’s method [25], Row 2 - Yoo’s method [34], Row 3 - Xu’s method [21], Row 4 - our proposed method. while handling the scenarios like lane change**. As can be seen in Fig. 10, graph is plotted for the trajectory of ego lane location, where x-axis denotes the frame numbers and y-axis represents the bottom-most x-coordinate of the detected left and right lane marking lines. Notably, the ego lane undergoes a rightward shift around the 40th frame, indicated by abrupt positional transitions for both left and right lane markings. At 40th frame number, position of left lane mark transits from point (a) to point (b), followed by the right lane mark transitioning from point (b) to point (c). Similarly, around 265th frame,the ego lane undergoes a leftward shift,where position of right lane mark shifts from point(d) to point (e), followed by the left lane mark transitioning from point (e) to point (f). Moreover, the figure provide insights into tracking outcomes for clip7, wherein detection with large deviation factor and measurement errors are also highlighted. For trajectories of other clips please refer VI-A 2) Caltech Dataset: Our proposed method is also applied on the Caltech Dataset [25] with sample results shown in Fig 12. Caltech Dataset consist of four clips: cordova1, cordova2, washington1 and washington2. Caltech dataset which include Fig. 10. lane change to right side is seen in sudden transition of left lane mark point from (a)to (b) and right lane mark point(b) to (c). Smilarly,during lane change to left side left lane mark point transits of points(d)to (e) and point(e) to (f) Fig. 11. Blue indicates detection result while green represents ground truth lane markings. Adjusting thresholds to t1 = 10 and t2 = 15 resolves the issue of false positives observed with thresholds of t1 = 15 and t2 = 20 marking like deflection arrows, word messages, bifurcation arrows, rectangular blocks, zebra crossing marks. Indian roads generally speaking does not have have much yellow markings. So, in order to capture yellow road marking,we empirically set the threshold band on H channel to 20◦ as lower bound and 65◦ as upper bound. Unlike previous approaches by Yoo [34] and Aly [25] that used t1 = 15 and t2 = 20, we chose t1 = 10 and t2 = 15 for the Caltech dataset. This is done since, upon assuming t1 = 15 and t2 = 20, a false positive detection (in blue) with respect to ground truth (in green) is observed in Fig 11. The selection of t1 = 10 and t2 = 15 effectively addresses this issue. Comparison of lane detection rate on caltech dataset is shown in Table II. Our method achieves a detection rate of 98.50% in mode2 and 93.75% in mode1, surpassing the rates of 91.60% and 89.40% achieved by Yoo’s and Aly’s methods, respectively, for cordova1. Despite the reliance of Yoo’s method on inter-frame similarity and Aly’s method detecting lanes in each frame independently, both exhibit a detection rate of 88.42% and 75.37% in cordova2. Introduction and discontinuation of parking lane marks in certain frames (from frame f00264 to f00314) result in abrupt shifts in reference lane markings position used to define ego lane, posing challenges for inter-frame similarity to address. Our method outperforms their performance with detection result of 93.84% in mode2, where mode1 is applied every 10th frame until stable detection results are obtained in full-frame JOURNAL OF LATEX CLASS FILES, VOL. 18, NO. 9, SEPTEMBER 2020 TABLE II C OMPARISON OF L ANE D ETECTION R ATE ON C ALTECH DATASET Clips Aly’s [25] Yoo’s [34] Our method Our method mode1 mode2 Cordova1 91.60 89.40 93.75 98.50 Cordova2 75.37 88.42 82.22 93.84 Washington1 92.43 83.97 91.10 95.76 Washington2 92.46 95.25 97.62 97.83 10 degree with Indian Institute of Science, India. Her research interests include image processing,pattern recognition and computer vision. As can be seen in Fig XXXX, lane markings features are difficult to extract because of strong saturation. Comparing the result with Aly[25], Yoo[34] and Xu’s[21] work, it is clear that our proposed method is outperforming their method. Experiment results in shadow, dark. 8) extraction of Lane marks considers both 1) their gray values (ii) location of lane marking 9)used only soft thresholding, carefully pruning lane marking features10) Defining the supposed even in the presence of vehicle ahead advances the scope the vehicle detection in the particular trajectory width consistency is also not the same, road can change the shape and change needs to be accepted,we cannot correct always on the basis of the other detected lane marking,new lane marking could be introduced and then DAOI fails, keep checking if new line is introduced. R EFERENCES Fig. 12. Lane detection results on caltech dataset samples: Row 1,2 - Aly’s method [25], Row 3,4- Yoo’s method [34], Row 5,6- our proposed method. mode, followed by re-establishment of DAOI with kalman filter re-initialization. However, absence of lane marking clues on the right side contributes to incorrect detection. Moreover, by effectively addressing lane changes, our method achieves a high detection rate of 95.50% as compared to 92.43% and 83.97% in Yoo’s and Aly’s work, respectively, for washington1. V. CONCLUSION Unlike the XXXXXXXXXXXXXXXXX method where is required, our method consider various innate properties of lane markings like statistical characteristic, geometrical shape and inter-frame similarity etc 3)Assumption is that lanes does not substantially change between consecutive two frames and the lane in t frame is estimated by using detecting lane in t-1 frame. It opens up the scope where any object in the ego lane Saumya Srivastava (S’14) received the B.Tech degree in Instrumentation and Controls engineering from Uttar Pradesh Technical University,India, in 2014 and the M.Tech degree from IIT-BHU in 2017. She is currently working toward the Ph.D. [1] Narote, S.P., Bhujbal, P.N., Narote, A.S. and Dhane, D.M., 2018. 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Lane recognition on poorly structured roads-the bots dot problem in California. In Proceedings. The IEEE 5th International Conference on Intelligent Transportation Systems (pp. 67-71). IEEE. 11 Fig. 13. chart shows the detection comparision done on various clips on our dataset Fig. 14. lane change to left side is seen for clip6 in our dataset.Sudden transition of left lane mark point from (a)to (b) and right lane mark point(b) to (c). Similarly,during lane change to left side left lane mark point transits of points(d)to (e) and point(e) to (f) VI. A PPENDIX A. Mathematical Typography and Why It Matters Fig 14 shows the trajectory of ego vehicle over 450 frames in clip6 (our dataset). Lane change embarks around 326th frame, with sudden transition of left lane mark point from (a)to (b) and right lane mark point(b) to (c). Similarly,ego lane shifts again to left side with right lane mark point transits of points(d) to (e) and left lane mark from point(e) to (f).Fig 16 shows the trajectory of ego vehicle over 350 frames in washington1 (caltech dataset).Ego lane shifts to left side around 100th frame, with sudden transition of left lane mark point from (b)to (c) and right lane mark point(a) to (b). B. Mathematical Typography and Why It Matters Data: IPM Image, mode t , xm , IFs pan, Iode0 = 1 for t = 1, 2, . . . , T ( T is the number of frames) do 1l xt , [α0 α1 α2 ]r , 1r xt = Detection (I , mode, xm ) C + DF = Deviation Factor 1l xt , cl xt , 1l x̂+ , x̂ if mod t−1 l t−1 (t/IF− span) == 0 OR mode t == 1 if DF < T P S JOURNAL OF LATEX CLASS FILES, VOL. 18, NO. 9, SEPTEMBER 2020 Fig. 15. lane change to left side is seen for washington1 in caltech dataset.Sudden transition of left lane mark point from (a)to (b) and right lane mark point(b) to (c). Similarly,during lane change to left side left lane mark point transits of points(d)to (e) and point(e) to (f) Fig. 16. lane change to left side is seen for washington1 in caltech dataset.Sudden transition of left lane mark point from (a)to (b) and right lane mark point(b) to (c). Similarly,during lane change to left side left lane mark point transits of points(d)to (e) and point(e) to (f) then mode t+1 = 2/∗ DAOI established 1for cnext frame + */ 1l x̂+ , x̂ ← Update kalman filter x , x else-if t l t l t l t 1 c 1 C x , x − x̃ , x̃ < threshold /* stable detection l t l t l t−5:t l t−5:t + ∗/ mode t+1 = 2 1l x̂+ ← Re-initialize kalman filter t , l x̂t + 1 c 1 + x , x else mode = 1 x̂ , x̂ ← kalman filter (large t+1 l t l t l t l t 1 c meas error) 1l x̃t−5:t , C x̃ ← Update MAWE l t−5:t l xt , l xt end if mod(t/IF− span) ̸= 0 OR mode t == 2 then if DF < T P S then 1: mode for next t+1 = 2 /* DAOI established C + 1 c frame ∗/ 2: 1l x̂+ , x̂ ← Update kalman filter x , t t l t l l xt 3: + result = 1l x̂+ else 1: mode t , l x̂t t+1 = 2/∗ DAOI established + for next frame ∗/ 2: 1l x̂+ , x̂ ← kalman filter (large meas t l t C + error) end return 1l x̂+ , x̂ t l t XXXXXXXXXXXXXXXXXXXXXXXXXXXX 12 Algorithm 1 An algorithm with caption Require: n ≥ 0 Ensure: y = xn y←1 X←x N ←n while N ̸= 0 do if N is even then X ←X ×X ▷ This is a comment N ← N2 else if N is odd then y ←y×X N ←N −1 end if end while JOURNAL OF LATEX CLASS FILES, VOL. 18, NO. 9, SEPTEMBER 2020 Data: IPM Image, modet , xm , IFspan , mode0 = 1 for t = 1, 2, ..., T (T is the number of frames) do 1 1 l xt , [α0 α1 α2 ]r , r xt = Detection (I, mode, xm ) + + DF = Deviation Factor(1l xt , cl xt , 1l x̂t−1 , C l x̂t−1 ) if mod (t/IFspan ) == 0 OR modet == 1 if DF < TPS then modet+1 = 2 /∗ DAOI established f or next f rame*/ + + 1 c (1l x̂t , C l x̂t ) ← U pdate kalman f ilter (l xt , l xt ) else-if (1l xt , cl xt − 1l x et−5:t , C et−5:t ) < threshold l x stable detection modet+1 = 2 C + 1 c (1l x̂+ t , l x̂t ) ← Re-initialize kalman f ilter (l xt , l xt ) else modet+1 = 1 + + (1l x̂t , C l x̂t ) ← kalmanf ilter (large meas error) 1 et−5:t , C et−5:t ) ← lx l x U pdate M AW E (1l xt , cl xt ) end if mod(t/IFspan ) ̸= 0 OR modet == 2 then if DF < TPS then 1: modet+1 = 2 / ∗ DAOI established f or next f rame ∗ / C + 1 c 2: (1l x̂+ t , l x̂t ) ← U pdatekalmanf ilter(l xt , l xt ) + + 3: result = (1l x̂t , C l x̂t ) else 1: modet+1 = 2 / ∗ DAOI established f or next f rame ∗ / C + 2:(1l x̂+ t , l x̂t ) ← kalmanf ilter( large meas error) end return C + (1l x̂+ t , l x̂t ) 13