Road Impact Assessment
Proposed Sand Extraction Development
Lot 1 Meehan Road, Cape Cleveland
REPORT FOR B M WEBB HOLDING PTY LTD
Report Reference: TWEB001/R01
Date: 14 December 2010
Revision: E
PO Box 1042, Townsville Qld 4810
Telephone: (07) 4772 0677, Facsimilie: (07) 4772 0566, Email: main@udphorman.com.au
ABN 15 138 608 296
UDP HORMAN TRAFFIC PTY LTD
1.
INTRODUCTION
B M Webb Holdings Pty Ltd (B M Webb) has proposed a sand extraction
development located on the existing parcel of land on Lot 1 on RP733021, Cape
Cleveland. Figure 1 shows the locality.
B M Webb proposes to extract and transport 1.19 million tonnes of sand from the
subject site in Cape Cleveland to the destination site in Webb Drive, Mount St John
between 2010 and 2032.
B M Webb has briefed UDP Horman Traffic (UHT) to undertake a Road Impact
Assessment (RIA) for the proposed development giving consideration to the safety
and operation of intersections along the proposed haulage route and the impact on
the pavement of state controlled roads (SCRs).
2.
THE PROPOSAL
B M Webb proposes to extract 1.19 million tonnes of sand over 22 years from the
subject site and haul it to Webb Drive, Mount St John. The extraction proposal
encompasses 47.51 Ha of land and is proposed to be carried out over 17 stages.
Stage sizes will vary from 1.87 Ha to 4.34 Ha.
Approximately 54,000 tonnes of sand will be transported annually by trucks with four
(4) axle dogs. Each truck and dog will carry approximately 35 tonnes of sand. B M
Webb advises that sand extraction operations are 12 hours per day, 5.5 days per
week, 48 weeks of the year. Therefore the proposal would generate 5.84 truckloads
per day. (54,000 t/yr ÷ 35 t/truck ÷ 5.5 days/wk ÷ 48 wk/yr = 5.84) For the purposes of
this investigation it has been assumed that six (6) truckloads will be generated.
Table 1 shows the characteristics for one proposed haulage vehicle and its pavement
impact (expressed in equivalent standard axles (ESAs)).
Table 1. ESA Generation for 19 m truck and 4-axle dog
19 m truck and 4-axle
Vehicle
dog
Austroads Class
10
Carrying Capacity
35 t
ESAs Loaded
8
ESAs Unloaded
<2
The proposed haulage will therefore generate 48 ESAs loaded (north bound) and up
to 12 ESAs unloaded (south bound) per day. The haulage route for the proposal is
shown in Figure 2.
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It should be noted that B M Webb currently acquires sand from other sand extraction
sites located in the same area. Therefore the proposed extraction operation will
enable B M Webb to extract their own sand without having to utilise other sites. Even
so, the analysis contained in this report conservatively assumes that all traffic
generated by the development is new traffic which was not previously on the SCR
network.
3.
ROAD IMPACT ASSESSMENT
3.1 Pavement Impact
Existing heavy vehicle (HV) traffic volumes on the sections of the haulage route were
taken from DTMRs 2008 Traffic Census Report (2008 Census). Note that stages 2
and 3 of the Townsville Ring Road (TRR) did not open until 2009. Therefore, existing
HV traffic on the TRR (including the Douglas Arterial) is expected to be significantly
higher than that reported in the 2008 Census (at the time of preparing this report
2009 Traffic Census data was not available.) It was assumed that one (1) HV as
reported in the 2008 Census would generate three (3) ESAs. Table 2 shows the
estimated number of ESAs generated by HV traffic on the relevant sections of the
SCR network, and the impact that the proposal would have on the road sections.
Table 2. Existing Heavy Vehicle Traffic ESAs on sections of SCRs
Road Section
HV Traffic (AADT)
(North / South)
HV Traffic
(ESAs)
(North / South)
% Impacta
(North / South)
700 m north of Allambie Lane
419 / 445
1257 / 1335
3.82 / 0.90
1 km west of Hunter Street
789 / 829
2367 / 2487
2.03 / 0.48
200 m west of Cluden Racecourse
794 / 784
2382 / 2352
2.02 / 0.41
150 m east of Lachlan Wilson Drive
848 / 897
2544 / 2691
1.89 / 0.45
1087 / 1191
3261 / 3573
1.47 / 0.34
b
200 m east of Mark Reid Drive
a
% impact is calculated relative to existing ESAs (in 2008).
heavy vehicle proportion was not recorded in the 2008 Census for this road section. Therefore the
previous road sections Heavy vehicle traffic was adopted.
b
Table 2 indicates that the proposal will increase the number of ESAs on the state
controlled roads by less than 5% and thus based on DTMR’s “Guidelines for
Assessment of Road Impacts of Development Proposals” (GARID) the impact is not
significant.
3.2 Intersection Operation and Safety
It is noted that Cape Cleveland Road (CCR) is the only access to Cape Cleveland
and this incorporates the majority of vehicles that access Carty Road and Meehan
Road. Also, the existing traffic volume on CCR is very low (<1000 vpd). It is therefore
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concluded in relation to the CCR / Carty Road and Carty Road / Meehan Road
intersections that even with the proposed development the total intersection entering
volume will remain very low and the impact on intersection operation will be
negligible.
3.2.1
Bruce Highway / Cape Cleveland Road Intersection
A 12 hour traffic count was conducted at the Bruce Highway / CCR intersection on 18
May 2010 to determine the existing traffic volumes entering / exiting CCR. Figure 3
shows the results. Figure 4 shows the estimated 24 hour traffic volumes at the
intersection. It was assumed that the 24 hour volumes are 1.25 times the 12 hour
volumes. The 24 hour traffic volumes indicate that less than 1,000 vpd are on CCR
and total intersection entering volume is less than 6,000 vpd. This is well within the
capacity of a T-junction with turning lanes.
Figure 6 shows the existing arrangement of the Bruce Highway / CCR intersection
which is located within the Bowling Green Bay National Park. The prominent feature
of the intersection is a level crossing that runs through the north eastern leg (CCR) of
the intersection. Note that traffic warning signals have been installed which include
angled repeater signals for traffic approaching CCR along the Bruce Highway from
the northwest.
Figure 7 shows photographs of the northwest, northeast and southeast approaches
from the centre of the intersection. These photographs indicate that sight distances at
the intersection are adequate.
In its current configuration, the intersection has insufficient queuing distance (after
the level crossing) for articulated vehicles (≥ 19 m) turning onto the Bruce Highway.
Figure 6 shows that there is approximately 14 m between the exclusion zone of the
crossing and the give way line at the Bruce Highway. This is of concern as there is a
risk that a train will collide with the rear of an articulated vehicle waiting to turn onto
the highway.
A number of options exist for managing this situation and include:
•
Acceptance of the current proposal;
•
Separation in time of conflicting movements (e.g. using traffic signals to control
the intersection and adjacent railway level crossing);
•
Separation in space of conflicting movement (e.g. grade separation of the right
turn from CCR onto the highway);
•
Use of an alternative haulage vehicle (e.g. single unit trucks); and
•
Use of an alternative haulage mode (e.g. rail).
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All options have their advantages and disadvantages in terms of safety, cost and
environmental impact. In comparing options for the management of the intersection
the following features of the intersection (as observed during the 12 hour count) are
relevant:
•
11 trains passed through the intersection in twelve hours;
•
293 vehicles turn right out of CCR in 12 hours with 15 of these vehicles being
articulated vehicles; and
•
The two-way traffic volume on the Bruce Highway past CCR is 3,962.
The risk of an accident occurring between two (2) conflicting modes is assumed to be
proportional to the square route of the product of the conflicting flows, i.e.
R = k * (V 1 *V 2 )1/2
R
k
V1
V2
= Risk of an accident.
= Constant of proportionality.
= Volume of vehicles in conflicting flow 1.
= Volume of vehicles in conflicting flow 2.
On this basis, the current risk of an accident occurring between a vehicle queuing
across the railway lines and a train is 13k rail and the risk of an accident occurring
between traffic turning right out of CCR and highway traffic is 1,077k T . Thus the total
risk of an accident at the intersection is:
R TOTAL = 13k rail + 1077k T
k rail = Constant of proportionality for accidents between vehicles queued at a
railway level crossing and trains.
k T = Constant of proportionality for accidents between vehicles turning right out
of a T-junction and through traffic on the major road.
Accept the Current Proposal
The current proposal will increase the number of articulated vehicles turning right out
of CCR from 15 in 12 hours to 21 and the total volume of traffic making this
movement from 293 to 299. Therefore the risk of an accident occurring between a
train and queuing traffic is 15k rail and the risk of an accident occurring between traffic
turning right out of CCR and highway traffic is 1088k T . Thus the proposed
development will increase the risk of an accident between a truck and a train by
about 15% and the risk of an accident between two (2) road vehicles by about 1%.
The total risk is
R TOTAL = 15k rail + 1088k T
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Separation in Time
Installing traffic signals should reduce the risk of an accident involving a truck and a
train to its minimum amount (assumed to be negligible) but the risk of an accident
occurring between traffic on the highway and CCR will be about 1088k signals .
According to statistical data from Victoria, signalised T-junctions in high speed
environments typically have 40% more accidents than unsignalised T-junctions
(i.e. k signals = 1.4*k T ). Thus the total risk is
R TOTAL = 1523k T
In order for the installation of traffic signals to be justified k rail would need to be
almost 30 times k T . This is considered unlikely and it is therefore concluded that the
installation of traffic signals at this location would reduce the intersections safety and
not improve it.
Separation in Space
The intersection could be grade separated by providing an overpass for traffic turning
right out of CCR. This would greatly reduce the conflict between CCR traffic and both
rail and highway traffic. This option would be expensive and have significant impacts
on the adjacent wetlands and hillside within Bowling Green Bay National Park.
Alternative Haulage Vehicles
Smaller haulage vehicles would be able to queue safely between the Bruce Highway
and the railway level crossing. Two (2) practical options exist for smaller haulage
vehicles being either 3-axle or 4-axle trucks. Reducing the size (and therefore
capacity) of the haulage vehicle would increase the number of trips required. Table 3
shows the trips required and the ESA’s generated for two (2) possible vehicle types.
Table 3. Haulage Vehicle Characteristics
Austroads
Class
Vehicle
Type
Maximum
Length (m)
Maximum
GCM (t)
Max ESA's per
vehicle
(fully loaded)
Trips
Required
Impact
ESA's
4-axle
12.5
27.5a
4.4
12
52.8
truck
3-axle
Class 4
12.5
22.5b
3.97
17
67.5
truck
GCM – Gross Combined Mass
a
Practical capacity for the 4-axle truck (17.5t) was assumed to be 50% of the GCM for the 4-axle truck
and dog
b
Practical capacity for the 3-axle truck (12.5t) was estimated assuming an unloaded 3-axle truck
weighs the same as an unloaded 4-axle truck, i.e 10t
Class 5
It is noted that the 3-axle trucks would have a slightly higher pavement impact than
the current proposal of truck and dog combinations. Therefore, for further analysis it
is assumed that 4-axle trucks are used. Using smaller haulage vehicles will have no
impact on the risk of an accident involving vehicles queuing across the railway line
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but will increase the risk of an accident involving vehicles turning out of CCR and
highway traffic to 1099k T . Thus the total risk of an accident would be:
R TOTAL = 13k rail + 1,099k T
If k rail is more than seven (7) times k T then the use of single unit trucks is safer than
the use of truck and dogs. However, if k rail is less than four (4) times k T , the safer
option is to use truck and dogs. Further analysis is required to distinguish between
these options.
The use of smaller vehicles will incur additional costs and produce increased
emissions relative to the current proposal.
Alternative Haulage Mode
It is noted that the component of the haulage route which uses SCRs is paralleled by
a railway line which offers an alternative haulage mode. This would completely
eliminate any impact of the proposed development on the safety, operation and
pavement of the SCR network. However, as with the overpass option, it is likely that
the cost and environmental impact of providing a rail siding in Bowling Green Bay
National Park will be significant. Unlike the overpass option, the benefits would go
almost entirely to the developer with no change to existing safety issues at the
intersection. This option would also disadvantage B M Webb due to the “double
handling” of material transported from the sand extraction sight to the railway line by
truck, then by train from Cape Cleveland to the Bohle and finally by truck again from
the railway line to Webb Drive.
Comparison of Options
Each option was given a rating from “A” to “E” for safety, cost and environmental
impact. Safety has been separated into that of the haulage vehicles and that of the
community in general. “A” is considered a major positive impact, “B” a minor positive
impact, “C” is similar to the status quo, “D” is a minor negative impact and “E” is a
major negative impact. The assessment is limited to the Bruce Highway / CCR Tjunction and adjacent railway level crossing. Table 4 shows the proposed ratings.
Table 4. Comparison of Options for Managing the Bruce Highway / Cape Cleveland
Road T-junction
Safety
C
Environmental
impact
C
E
D
C-
A
A
E
E
4-axle trucks
B
C
C-
C-
Haulage by rail
A+
C
E-
D
Option
Haulage
C
Community
C
Traffic signals
E
Grade separation
Current proposal
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From the above table it is concluded that the use of traffic signals is unacceptable as
it will reduce the intersections safety. Also, grade separation and haulage by rail are
considered unacceptable as they are likely to have significant environmental impacts.
It is therefore recommended that the development proceed with no change to the
Bruce Highway / Cape Cleveland Road T-junction and haulage by either 4-axle
trucks or truck and dog combinations. Of these two (2) options haulage by truck and
dog combinations will be the slightly better option in economic and environmental
terms. There is little difference between these options in terms of intersection safety
for the community.
3.2.2
CCR / Carty Road Intersection
The CCR / Carty Road intersection is a standard sign controlled T-junction. Given the
open terrain and straight roads of the intersection there is sufficient sight distance in
all directions for approaching traffic. Also, the intersection geometry is sufficient to
accommodate heavy vehicles turning.
From a review of the Cape Cleveland road network it is estimated that the traffic
volume entering this intersection will be similar to that on Cape Cleveland Road at
the Bruce Highway, i.e. about 1,000 vpd. This is a very low volume and the operation
of the intersection is not likely to be affected adversely by the additional ten (10) trips
per day generated by the proposed development.
3.2.3
Carty Road / Meehan Road Intersection
The existing condition of Meehan Road is currently a rural unsealed road. This will be
required to be upgraded to a bitumen sealed road as per the City Plan as a result of
the proposed sand extraction industry.
The volume of traffic entering the Carty Road / Meehan Road intersection is assumed
to be very low given the volume of traffic observed on CCR. As such the effect on the
operational capacity of the intersection will be negligible.
Figure 8 shows the eastern and western approaches to the intersection. There may
be an issue with respect to the eastern approach sight distance due to the moderate
bend and dense vegetation. This may require periodic pruning of the vegetation.
4.
SUMMARY AND CONCLUSION
B M Webb proposes to extract 1.19 million tonnes of sand over 22 years from the
subject site located on the existing parcel of land on Lot 1 on RP733021 to its
destination in Webb Drive, Mount St John. The Townsville Ring Road has been
proposed as the principle haulage route for the sand extraction proposal. It has been
concluded that the ESA’s generated by the proposal will not significantly impact state
controlled roads.
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The development will generate 12 vehicle movements per day. This will not
noticeably impact on the capacity or operation of any intersections or road links.
It has been found that there is only 14 m of storage space available in CCR between
the Bruce Highway and adjacent railway level crossing. Therefore, the rear of an
articulated vehicle waiting to turn on to the highway will not be clear of the railway
line. This is a potential safety issue and existing deficiency with the intersection. A
number of options exist for managing this situation and include:
•
Acceptance of the current proposal;
•
Separation in time of conflicting movements (e.g. using traffic signals to control
the intersection and adjacent railway level crossing);
•
Separation in space of conflicting movement (e.g. grade separation of the right
turn from CCR onto the highway);
•
Use of an alternative haulage vehicle (e.g. single unit trucks); and
•
Use of an alternative haulage mode (e.g. rail).
It is concluded that the use of traffic signals is unacceptable as it would reduce (not
improve) the intersection’s safety. Also, grade separation and haulage by rail are
considered unacceptable as they are likely to have significant environmental impacts.
It is therefore recommended that the development proceed with no change to the
Bruce Highway / Cape Cleveland Road T-junction and haulage by either 4-axle
trucks or truck and dog combinations. Of these two (2) options haulage by truck and
dog combinations will be the slightly better option in economic and environmental
terms. There is little difference between these options in terms of intersection safety
for the community.
The CCR / Carty Road and Carty Road / Meehan Road intersections provide
adequate capacity, geometry and sight distance to operate safely and efficiently to
serve quarry traffic without modification. It is possible that vegetation on the inside of
a curve to the east of Meehan Road will restrict visibility at the Carty Road / Meehan
Road intersections and may require periodic pruning.
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FIGURE 1
LOCALITY PLAN
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FIGURE 2
PROPOSED HAULAGE ROUTE
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FIGURE 3
12hr OBSERVED TRAFFIC VOLUMES
FIGURE 4
24hr ESTIMATED TRAFFIC VOLUMES
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TURNING MOVEMENT DIAGRAM SHOWING VEHICLE CATEGORIES
LOCAL
INTERSECTION:
AUTHORITY:
BRUCE
TOWNSVILLE HIGHWAY/CAPE
COUNCIL
CLEVELAND
ROAD
DAY
7AM7PM
DATE:
17MAY-10
TUESDAY
AM PEAK
9:15 AM
TO
10:15 AM
PM PEAK
4:00 PM
TO
5:00 PM
NORTH
POINT
WEATHER
OVERCAST
Cape Cleveland Road
Light
Vehicle
312
1540
Bus and
Trucks
13
133
Articulated
Vehicle
14
216
Light Vehicle
263
16
Bus & Trucks
15
1
Articulated Vehicle
15
2
Bruce Highway
Bruce Highway
Light
Vehicle
23
1612
Bus and
Trucks
0
133
Articulated
Vehicle
1
304
FIGURE 5
CCR / BRUCE HIGHWAY INTERSECTION 12 HOUR VOLUMES
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5.5m
75m
5.5m
14m
75m
FIGURE 6
BRUCE HIGHWAY / CCR INTERSECTION (EXISTING)
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South-west Approach
North-west Approach
North-east Approach
FIGURE 7
CCR / BRUCE HIGHWAY INTERSECTION
APPROACHES (EXISTING)
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Eastern Approach
Western Approach
FIGURE 8
CARTY ROAD / MEEHAN ROAD INTERSECTION
APPROACHES (EXISTING)
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