Example of Road Safety Audit

Transport Systems Engineering

Road Safety Audit

Part 1 – 1.0 Road Safety Audit

            1.1 Task 1: Identification and ranking of potential safety issues:

The following table is an in-depth description of the potential safety issues regarding the road, road signs, line markings and the surrounding landscape on a section of Sir Fred Schonnel Drive between Coleridge St and Gailey Rd (approx 1.3Km long). Included in this section are four major intersections and one roundabout. Along with the locations of these safety issues will be the various types of crashes that can be expected to occur at these sites as well as their various risk factor.

·       Table 1. Identification of potential safety issues

LOCATION

ISSUES

CRASH TYPES

RISK FACTOR

282 Sir Fred Schonnel Dr

- App. Roundabout

- Good sight distance

- No blocking views

- Kerb blister approach and exit

- Good deflection

- Easy to interoperate signage

- Separate lane for cyclists

- Clear line markings

301, 708, 102, 808, 303, 104, 105, 205

High Risk

Munro St exit

- Mountable roundabout for busses. Etc

- Path leading onto road but no zebra crossing.

808, 302, 002, 008, 003,

High Risk

244 Sir Fred Schonnel Dr

- Two lane exist one lane entry

- Long merging lane, tapers off very quickly though.

306

Low Risk

235 Sir Fred Schonnel Dr (and throughout section)

- No standing sign

- Unbroken centre line, stopping overtaking.

305, 601, 604

Low Risk

220 Sir Fred Schonnel Dr (and throughout section)

- Numerous entries to private property from the main road.

406

Extremely High Risk

207 Sir Fred Schonnel Dr

- Signalised int.

- Four lights facing each direction

- Designated pedestrian crossing

- Good line markings and signage

301, 202, 203, 204, 101, 102, 104

Medium Risk

202 Sir Fred Schonnel Dr

- Bus stop directly after traffic lights

- Also before ‘T’ intersection

- Bus takes up full lane when stopped

506, 301, 401, 503

Extremely High Risk

187 Sir Fred Schonnel Dr

- More no standing signs

601

Low Risk

179 Sir Fred Schonnel Dr

- Turn in road

- Good signage indicating curve and reduce speed

- Hill and bus stop before curve

805, 601, 503

High Risk

155 Sir Fred Schonnel Dr

- First speed sign seen on road

Low Risk

Cnr of Sir Fred Schonnel Dr and Brisbane St

- Signs indicating curve in road

- Guard rails along the left side of curve

- At intersection poor site distance in both directions as approach is on a hill.

- Guardrails split into two sections leaving 2m gap in the middle.

801, 805, 302, 101

High Risk

150 Sir Fred Schonnel Dr

- Large tree hanging low and covering one half of road

610

Medium Risk

134 Sir Fred Schonnel Dr

-No stop or give way signs or line markings visible

- Good visibility on approach

101, 102, 303

Medium Risk

Sir Fred Schonnel Dr and Bryce St

- ‘T’ intersection onto main road

- Clear line markings

- Good visibility in only one direction

101, 102, 302

Medium Risk

121 Sir Fred Schonnel Dr

- Bus stop

- When bus stopped takes up full lane on a downhill section

301, 401, 601, 503

Extremely High Risk

Throughout

- Constant lighting along complete section of road

Low Risk

95 Sir Fred Schonnel Dr

- Approach to intersection

- Four lights facing each direction

- Western approach one of these lights not working

- Signage indicating no right turn

-Pedestrian crossing, line markings

-No right or left turn arrows

301, 202, 302, 203, 204, 102, 101, 104

Medium Risk

76 Sir Fred Schonnel Dr

- Bus stop directly after and before major intersection traffic lights

301, 401, 601, 503

High Risk

66 Sir Fred Schonnel Dr

- Good vision at intersection both ways

- Give way markings wearing away

- Kerb deflection markings present

101, 102, 302, 107

Medium Risk

Throughout

- Heavy build up of dense foliage on either side of road, makes difficult to see when turning onto main road from side street.

-Numerous driveway entrances that go straight onto main road possess problems for cars slowing to down to get in and reversing out.

101, 102, 302, 107

High Risk

17 Sir Fred Schonnel Dr

- Bus stops right before major intersection

- Blocks entire lane including designated left hand turning lane

- No stop signs present

101, 102, 302, 104

High Risk

9 Sir Fred Schonnel Dr

-Major ‘T’ Intersection

- Good turning lane markings

- Four traffic lights facing each way

- Kerb blister (islands) in place

- Slip lanes separated by islands

- Adequate sight distance and deflection kerbs on either side

- Traffic signs present

-  Slip lane merges onto majority turning lane from opposite direction

108, 301, 302, 102, 001, 002, 107

High Risk

A special note from this table must be given to the crash type section, this column indicates purely the different crash types that could potentially occur at the various sites not necessarily the likelihood of them occurring. For this reason a site may have six- eight different crash types but still only be of medium risk whereas another site may have only two but be of high-extremely high risk.

With the information gathered from being out on location and identifying the various sites that pose a potential crash risk, it can be clearly seen that several areas need close attention to rectify some very serious issues on the section of road under review. Areas such us foot-paths leading onto a busy roundabout but no pedestrian crossing, buses stopping several times along the stretch of road (taking up an entire lane), traffic lights that aren’t working, line markings faded away, entrances/exits to private property from main road, overgrown shrubbery blocking view of road and improper guard rail design. All of these issues pose a high-extremely high risk to motorists, pedestrians and cyclists.

Part 1 – 1.0 Road Safety Audit

            1.2 Task 2: Identification of potential countermeasures:

·       Table 2.  Identification of all relevant DCA’s countermeasures and their reduction %

Identified DCA’s 002, 003:

For intersections:

·       New traffic signals (no turn arrows) 30

·       New traffic signals with turn arrows 30

·       Remodel signals 30

·       Grade separation 70

·       Improve sight lines 30

·       Street closure (one leg of cross intersection)

·       Street closure (close stem of tee)

·       Improve lighting 30

·       Ban parking adjacent to intersection 30

·       Extend median through intersection 50

For non-intersections:

·       Median or existing carriageway 50

·       Pedestrian refuge 50

·       Pedestrian (zebra) crossing 40

·       Pedestrian overpass 90

·       Pedestrian signals 70

·       Pedestrian crossing lighting 60

·       Improved route lighting 30

·       Clearway parking bans 30

Identified DCA’s 101, 102, 104, 105, 107, 108:

For intersections:

·       Roundabout 70

·       New traffic signals (no turn arrows) 70

·       New traffic signals with turn arrows 70

·       Remodel signals 30

·       Grade separation 100

·       Improve sight lines 30

·       Street closure (one leg of cross intersection) 50

·       Street closure (close stem of tee) 100

·       Stagger cross intersection (right – left) 50

·       Improve/reinforce priority (eg add a control sign) 30

·       Ban parking adjacent to intersection 10

·       Extend median through intersection 100

Identified DCA’s 202, 203, 204 205:

For intersections:

·       New traffic signals with turn arrows 45

·       Remodel signals 40

·       Grade separation 50

·       Improve sight lines 30

·       Street closure 50

·       Indented right turn island 30

·       Painted turn lane 20

·       Extend median through intersection 100

For non-intersections:

·       Indented right turn island 30

·       Painted turn lanes 20

Identfied DCA’s 301, 302, 303:

For intersections:

·       Non skid surface 40

·       Indented right turn island 40

·       Painted turn lane 20

·       Ban parking adjacent to intersection 20

·       Reduce radius on left turn slip lane 50

·       Protected left turn lane in crossing street

For non-intersections

·       Clearway, parking bans 20

·       Indented right turn island 40

·       Painted turn lanes 20

·       Non-skid surface 40

Identified DCA’s 305, 306:

For intersections:

·       ban parking adjacent to intersection 20

Identified DCA’s 401, 601:

For intersections:

·       Traffic islands on approaches 10

·       Indented right turn island 20

·       Painted turn lane 20

·       Ban parking adjacent to intersection 50

For non-intersections:

·       Clearway, parking bans 50

Identified DCA 801:

For non-intersections:

·       Roadside hazards – guard fence 30

·       Non-skid surface 10

·       Seal shoulders 40

·       Advisory speed signs on curves 30

·       Delineation 15

·       Edge-lines 30

·       Reconstruct super-elevation on curve 50

Identified DCA 805:

For non-intersections:

·       Non-skid surface 10

·       Seal shoulders 40

·       Advisory speed signs on curves 30

·       Table 3.  Potential countermeasure recommendations

282 Sir Fred Schonell Dr

- App. Roundabout

·       Removing the Coleridge Street exit from the park would reduce traffic from Munro Street into the roundabout.

·       Removing curbside parking adjacent to Coleridge Street roundabout would reduce likelihood of crashes occurring as parked cars exited car park.

·       Large sign advertising the University of Queensland slightly impedes driver visuals when entering roundabout from Coleridge Street and checking oncoming traffic to their right.

·       Also Information booth also impedes driver line of sight as they enter the roundabout from Coleridge Street.

244 Sir Fred Schonell Dr

·       Instead of having a merging lane, the lane should be continued/extended into the roundabout with the left approach consisting of a turn left/straight ahead marking, and the right approach with a straight ahead/right turn marking.

·       The left approach could then end at the campus side of Sir Fred Schonell Drive and in effect be a slip lane.

·       This accounts for the predominant traffic heading straight through the roundabout to the university to the parking facilities, and the secondary number of vehicles heading right at the roundabout to the colleges and other parking facilities etc.

220 Sir Fred Schonell Dr (and throughout section)

·       Effort needs to be made to maximize visibility for exiting vehicles from residential areas/apartments etc.

·       Introduction of road signs signaling through traffic to predominantly use right lane, and for residential vehicles/buses to use left lane so as to minimize stoppages and potential merging of traffic and consequential points of conflict.

207 Sir Fred Schonell Dr

- Signalised int.

·       Bus stop situated immediately after signalized intersection should be moved so as to minimize stoppages of traffic in the middle of the intersection when bus is attending (picking up/offloading) to passengers.

·       Traffic stopped at intersection may have to stop again to accommodate for bus stoppages at bus stop.

202 Sir Fred Schonell Dr

·       Bus stop situated immediately after signalized intersection should be moved so as to minimize stoppages of traffic in the middle of the intersection.

·       Traffic stopped at intersection may have to stop again to accommodate for bus stoppages at bus stop.

·       Slip lane/designated bus stopping lane for bus should be incorporated into side of road so as to minimize stoppages of vehicles.

Cnr of Sir Fred Schonell Dr and Brisbane St

·       Road gradient should be minimized so as to reduce blind spots.

·       Additional speed signs should be installed, as before and after that corner there are fairly straight stretches of road where vehicles can potentially build up speed unsuitable for entering that particular corner.

150 Sir Fred Schonell Dr

·       Tree should be trimmed so as to maximize visuals as road is on a decline as one heads to campus, thus reducing the visual capacity of drivers as they look at the road conditions ahead of them.

·       Trimming the tree would result in a clear roadway for all incoming vehicles maximizing viewing distance.

·       This is also a potential site for new bus stop with integrated slip lane, as park is easily able to make way for a bus stop as compared to alternative sites with pre-existing residential housing units.

134 Sir Fred Schonell Dr

·       Raven Street merge onto Sir Fred Schonell drive has minimal sighting of oncoming traffic hailing from campus.

·       Installation of warning signs for vehicles on Sir Fred Schonell Drive should be put in place warning of Raven Street traffic.

·       Mirrors should be installed for the benefit of Raven Street vehicular traffic thus reducing blind spots.

121 Sir Fred Schonell Dr

·       Bus stop needs to be relocated as it takes up a whole lane of traffic when stopping to take on passengers.

·       This stop is a suitable candidate for relocation to a potential slip lane bus stop incorporated into the pre-existing park area further up the street in the direction of campus.

·       At the moment, when buses are stopping at the bus stop they are blocking the line of sight of vehicles entering Sir Fred Schonell Drive off Bryce Street.

95 Sir Fred Schonell Dr

- Approach to intersection

·       Road gradient needs to be minimized to provide maximum line of sight to all vehicles entering the intersection.

·       Warning signs need to be put in place to warn drivers that there is a bus stop just over the ridge.

76 Sir Fred Schonell Dr

·       Bus stops should not be placed on opposite sides of road as when 2 buses are picking up/dropping off passengers at a simultaneous this severely minimizes the mine of sight of all vehicles.

·       Bus stop just before intersection invites stoppages in traffic and merging of traffic when there is a green light at the intersection and when a bus is stopping to attend to passengers.

Throughout

·       Need to eradicate excessive foliage so as to provide better line of sight to all vehicles, cyclists and pedestrians as road has steep and varying gradients and is also a very high use road.

17 Sir Fred Schonell Dr

·       Bus stops should be demolished as they are situated at 1) a designated left turning lane coming into a major intersection and 2) just after the Coronation Drive/Sir Fred Schonell Drive intersection which is one of, if not the main entrance point for all vehicular traffic heading to campus.

·       Having bus stops situated at the sites creates stoppages in traffic, forced merges of traffic, and dramatically increases the possibility of a number of types of collisions.

·       When bus is stopped all oncoming traffic coming off the Coronation slip lane coming into Sir Fred Schonell are forced to merge into one lane to accommodate for the bus stoppages.

Part 2 – 2.0 Investigation of Crash Locations 

2.1 Task 3: Assessment of road safety problems experiences:

The crash data from the year 2004 to the year 2008 was evaluated. In this data a total of 50 crashes were recorded.

Severity: From the data it can be seen that 22 incidents occurred that resulted in no injury to the individuals involved but resulted in property damage. This is the most common type of severity. Therefore it is important to focus on this area. However, the most severe crashes occurring in this period are crashes that resulted in the hospitalization of one or more of the individuals involved. This type of severity occurred 9 times over the five year period. It is important also to focus on this area as the risk to human life and well-being is the most important factor to focus on when dealing with road safety. There were also 9 crashes that resulted in hospitalization as an inpatient and 10 that resulted in minor injury that required no more than first aid.

Year: The number of crashes over any given year remains fairly constant with 8 crashes in 2004, 11 crashes in 2005, 12 crashes in 2006 and 9 crashes in both 2007 and 2008. This indicates that the year is not a contributing factor to the crash rate or the safety problems. It can be deduced that no significant changes occurred to the road in this time.

Month: Month seemed to have little to no effect on the crash rate and thus there are no safety problems caused by the changing months.

Day: The bulk of the crashes occur during the week. On the weekends only 9 crashes were recorded.  

Time: 19 crashes occurred between 6 and 10am. And, 13 crashes occurred between 1 and 5pm. This indicated that a significant number of crashes occurred between the university’s peak hour periods. This corresponds to the arrival and departure of users. This is a condition that cannot be controlled but indicates that the road may not be adequate for its users during these times.

Roadway Feature: Crashes occur evenly on the intersections and the road therefore it can be seen that both features contribute to the crash rate and occurrence of safety problems.

Horizontal Alignment: Crashes occurred both on the straight and curved horizontal alignment. However, the straight alignment resulted in more crashes with 41 crashes occurring with this feature. Therefore the safety problems are more likely to occur in these locations.

Lighting: Fewer crashes are present during the darkness and dawn/dusk periods than the daylight periods. This indicates that the street lighting is adequate during the dark periods. Also, at some periods during the day the sun interferes with the visibility of the road user, making crash occurrences more likely. 

Atmospheric Conditions and Road Surface: The majority of crashes occur during clear weather where the surface is sealed and dry. This indicates the presence of a safety problem. The crashes that occur during the raining conditions may indicate that the surface is not adequate during this time as is thus, a safety problem.

·      Table 4. DCA Codes

DCA Code &

Description

Causes identified in Chapter 8: Table 9.1

Causes found in site inspection

001

*Pedestrian on foot

*Near side

*pedestrian operated signals

*adequacy of zebra crossing

*jay walking

*parking inhibiting pedestrian sight lines

*adequacy of existing walk and don’t walk intervals

*street lighting

*speed limit

- Path leading onto road but no zebra crossing

-no auxiliary lanes for turning traffic

- frequent stopping by buses

-obstruction of sight at intersections by buses

-limited safe crossing options but frequent addition of pedestrians’ by bus stops.

201

*Vehicle in opposite direction

*Head on

*adequacy of centreline marking

*delineation of the curve

*restricted visibility

* local widening that looks like an overtaking lane.

*separation of opposing flows

*inadequate overtaking opportunities

*delineation, median, median barrier

*design, signs and lighting at intersections.

*speed limit

-not all curves intuitive

-restricted visibility at certain times of day

- separation by lane markings only

202

*Vehicle in opposite direction

*Through right

* sight distance available

*driver’s view drawn to a distant feature, past the intersection.

* day and night visibility of traffic control devices

*inadequate warning signs and devices.

*At unsigned T junction, no Give Way sign.

* street lighting.

* inadequate median islands

*function of two roads

*alignment of approaches at roundabout

*traffic light signals

* no mast arm at existing signals.

* At angled T-junctions, no hazard board opposite junction.

* diameter of traffic signals, inadequate overhead mast arm, no red light safety cameras and no supplimenatary advance flashing yellow warning lights.

*speed limit

- Four lights facing each direction

- Western approach one of these lights not working

- Signage indicating no right turn

-No right or left turn arrows

-sight distance inadequate for turning at top of hill

301

*Vehicle from one direction

*rear end by vehicle in same lane

* queuing by uninvolved right turn vehicles

*lighting.

* skid resistance and pavement drainage

*stopping distance at intersection, to the ‘tail of queue’

*adequacy of yellow phase or all-red clearance time

*offset timing

* ‘see through’ effect of a distant green and near red signal

*speed limit

-queuing

- no auxiliary lane

302

*Vehicle from one direction

* left rear

*no protected right/left turn auxiliary lanes or extend existing ones.

*right turns

* intersection angle of the lane with the intersecting road is not a minimum of 70 degrees

*skid resistance is poor

*speed limit

- Signs indicating curve in road

- ‘T’ intersection onto main road

- Good visibility in only one direction

-No right turn arrow at intersection

303

*Vehicle from one direction

*right rear

See 302

406

*Manouvering

*leaving driveway

See 202

- Numerous entries to private property from the main road.

601

*on path

*into parked car

* Parking on street

* Indent parking

* angle parking

*not adequate clearance between the

parking and through traffic lanes.

* Delinieatation of the edge of traffic lane past the parking area.

* street lighting.

*speed limit

- No standing sign

- Turn in road

- Hill and bus stop before curve

- Bus stop

- When bus stopped takes up full lane on a downhill section

- Bus stop directly after and before major intersection traffic lights

703

*off path on straight

*left off carriageway into object

* inadequate delineation

* alignment design and superelevation at isolated curve

* Widen the lanes or seal the shoulders.

*signs and advisory curve speed signing at critical curves.

*edgeline on curves.

* street lighting.

* surface texture, skid resistance and pavement drainage.

* speed limit

- curves not always intuitive

-Signs indicating curve in road

- Guard rails along the left side of curve

- At intersection poor site distance in both directions as approach is on a hill.

- Guardrails split into two sections leaving 2m gap in the middle.

-numerous entries onto property

-trees and poles close to road

            

Part 2 – 2.0 Investigation of Crash Locations 

2.2 Task 4: Proposed treatments to address safety problems identified.

There are many types of crashes identified in the crash data and thus there are many safety problems. The proposed treatments will focus on the issues that result in the highest level of harm to the road users.

Proposed Treatments for Crash (using Table 9.6: Effectiveness of countermeasures for intersection crashes):

001: It can be seen that this type of crash is a risk whenever pedestrians’ attempt to cross the road anywhere other than a designated crossing. The most obvious of these occurs at the Sir Fred Schonell Dr Roundabout where the footpath guides users to the road but does not offer a safe means to cross. A Zebra Crossing reduces the risk by an estimated 40% and a Pedestrian Refuge reduces the risk by 50%. A pedestrian overpass could be considered as it reduces the risk by 90% but the suburban environment is not receptive to this option and the cost associated with it is high.

201: This crash can be seen to occur when there is inadequate separation of opposing flows and inadequate delineation of curves. Reconstructing the super-elevation on the curve reduces the head on crash by 50%. In areas where intersections are a problem extending the median through the intersection reduces the head on crash by 100%, while also reducing the pedestrian crash by 50%. Seal shoulders and advisory speed signs on curve also reduce the head on crash by 40 and 30%.

 202: It was indentified that this type of crash can occur at the signalized intersections along Sir Fred Schonell Drive. At the western approach it was seen that one of the lights not working, this would have to be fixed before any alterations were considered.  It was also seen that the sight distance was inadequate at the top of the hill for turning right. This may be combated by the installation of a right turn arrow as discussed in 303 and 302.

301: It can be seen that this crash has the potential to occur when users wish to turn into side streets and when users wish to turn at intersections. A proposed treatment could be to widen the road and form auxiliary lanes where necessary. A limiting factor to this suggestion is the resumption of land required. A painted turn lane could also be considered as it reduces the risk of crashes involving opposing turns, rear end and parked vehicles by 20% each.

302 and 303: This crash can be seen to occur at intersections and when users wish to turn into adjacent streets. In the site inspection this was seen at the ‘T’ intersection and at the intersection at 95 Sir Fred Schonnel Dr. A treatment could be the addition of a right and left turn arrow so that users are not required to assume others actions. This reduces the crash involving the opposing turns by 45%, the adjacent approach crash by 70% and the likelihood of hitting a pedestrian by 30%.  Also protected right/left turn auxiliary lanes could be added (the limitations of which have already been discussed in 301).

406: This crash can be seen to be caused by the large number of residential properties along the road. This could be reduced by the removal of any obstructions to the sight distance. This however, is a problem that can only be controlled by the property owner. Though, education on this matter could be considered. Another option is the addition of an auxiliary lane or the widening of the lane (as discussed in 301).

601: It can be seen that this crash can occur when there are cars parked on the street. The site already has ‘no standing’ signs in place for certain times of the day. It may be considered to ban parking completely as the driver has to change lanes completely to overtake a parked car. This reduces the rear end crash by 20%, the pedestrian crash by 30% and the hit parked vehicle crash by 50%. Another cause of this may be the frequent stopping of buses along the road especially before and after intersections. By moving these bus stops and thus banning parking adjacent to intersections, this reduces the parked car crash by 50% as well as other crashes from 10 to 30%.

703: It was identified that this crashcould occur at curves in the road, at the guard rail and where the numerous entrances to properties and features such as poles and trees occur. This could be combated by improved alignment design through improved delineation and edge-lines. Delineation decreases the crash by 15% for all of the crash factors and edge-lines decrease the off road factors by 30% .  Removal of road side hazards is also an option; this however, reduces the risk of hitting the object by 80% but increases the chance of an off road crash by the same amount.

Other Treatments: It is important to note that in this study the focus has been on evaluating the road conditions. Any recommendations made only account for two out of the four components of a traffic system: speed and road environment. The other components, user and vehicle, were not discussed and it is advisable that this be looked into. For example, as the site is leading to a university many drivers may be inexperienced and this could be a contributing factor to the crash rate. Also there may be a likelihood of older, less safe cars being driven by inexperienced drivers. There also may have been a deficiency in the data. Incidents such as those involving bicycles may not have been considered or recorded as traffic safety problems.

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