Analyzing Road Segments for Bridge Presence
In order to understand the correlation between water accumulation on highways due to heavy rain events,
especially around bridges in the North Rhine-Westphalia (NRW) region of Germany, we used highway
network data for NRW along with bridge statistics from the Bundesanstalt für Straßenwesen (Federal
Highway Research Institute).
Using the highway line data in QGIS, we first merged all the line features into a single geometry. After that,
we dissolved the merging points and split the road into segments of 200 meters each. This segmentation
was done to assess the potential influence of a bridge on water accumulation at a specific road section.
Once the roads were split into 200 m segments, we created buffers around each segment — extending
14.5 meters on each side. to represent the actual width of a typical freeway. Using these buffered
segments along with the bridge dataset, we performed a spatial join based on intersection to determine
how many bridge points fell within each road segment.
Then, using the attribute table and field calculator, we created a new field that assigned either “Yes” or
“No” to each segment depending on whether it contained one or more bridges. We also assigned a unique
segment ID to distinguish between the segments.
In the end, we produced a layer of 200-meter road segments, visually marked in red or green to indicate
the presence (“Yes”) or absence (“No”) of bridges within each section, as shown in Figure 1. This output
can support further analysis of potential road damage caused by water accumulation during extreme
rainfall events.
Figure 1: Highway layout with bridges
Next actions:
- Tunnel
Velocity,
Flow depth
Flow velocity
Culvert
NDVI
Slope
Barriers/ laärmschutz - download DSM
References:
1- Bundesanstalt für Straßenwesen (BASt). (n.d.). Statistik – Ingenieurbau. Retrieved June 21, 2025,
from https://www.bast.de/DE/Ingenieurbau/Statistik/statistik-node.html