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03

"How-to" road safety solutions

Authors: Michael Tziotis, Suzy Charman, Claudia Adriazola-Delgado, Geert van Waeg, Steve Lawson, Mike Dreznes, Susanna Zammataro, Hans Vollpracht, Ceri Woolsgrove, Victoria Marlene Smith, Catherine Willis

1. The Global Safety Problem

1.1 Treating ‘high’ crash locations

The objective in the treatment of crash location is to reduce the incidence and severity of crashes at high crash locations. Fundamental to this objective is the requirement that the treatments match the crash problem, and that the remedial measure/s are proven and cost-effective (PIARC 2015).

1.2   Providing a Safe System Road Network

Identifying and treating road elements which may contribute to crash occurrence or crash severity is a major component of the Safe System approach to road safety. Adopting a Safe System approach to road safety recognizes that humans, as road users, are fallible and will continue to make mistakes, and that the community should not penalize people with death or serious injury when mistakes do occur. In a Safe System, therefore, roads (and vehicles) should be designed to reduce the incidence and severity of crashes when they inevitably occur.

The Safe System approach requires, in part:

  • designing, constructing and maintaining a road system (roads, vehicles and operating requirements) so that forces on the human body generated in crashes are generally less than those resulting in fatal or debilitating injury
  • improving roads and roadsides to reduce the risk of crashes and minimise harm: measures for higher speed roads including dividing traffic, designing ‘forgiving’ roadsides, and providing clear driver guidance. In areas with large numbers of vulnerable road users or substantial collision risk, speed management supplemented by road and roadside treatments is a key strategy for limiting crashes
  • managing speeds, taking into account the risks on different parts of the road system.

 

1.3 Use of this guide

The purpose of this guide is to provide road safety practitioners with a ready reference to remedial treatment options for known crash problems. The solution options have been selected on the basis of sound evaluations that have demonstrated their safety benefits. The degree to which they have shown themselves to reduce crashes, expressed as either a Crash Reduction Factor (CRF), i.e. expected % reduction in crashes, or Crash Modification Factor (CMF), i.e. expected number of crashes, may vary across countries (Elvik et al 2009). 

The solution selected will ultimately depend upon available budget, prevailing site factors, treatment cost, CRF or CMF and economic worth of the treatment (i.e. Net Present Value and Benefit Cost Ratio).

What this guide is not: it is neither an advocacy tool for specific road safety treatments nor a strategic road safety directions document.

1.4 Remedial treatment options, treatment life and indicative cost of treatments

The remedial treatment options provided in the guide and the effectiveness of these treatments have been drawn from two key internationally recognised resources, namely:

  • Elvik, R, Hoyes, A, Vaa, T, and Sorensen, M (2009). The Handbook of Road Safety Measures 2nd Ed. UK.The reference collates and summarises the findings of road safety research conducted by a vast number of researchers (which could include Elvik et al.), internationally across 128 road safety measures. Its main purpose is to provide "as objectively as possible the effects of road safety measures on road safety."
  • Road Safety Toolkit[1]: http://toolkit.irap.org

The Road Safety Toolkit was also used to estimate the life of the treatment options and the cost to implement them. Other references where used to supplement Elvik et al. CRF and/or CMF are also provided as required.

[1]The development partners of the Road Safety Toolkit were the World Bank Global Road Safety Facility, iRAP, ARRB Group and gTKP.

1.5 Multiple treatments

There may be cases when more than one treatment will be implemented at the one location. For example, on a bend of a road where drivers run-off the road, and where site investigations provide justification, treatments may include the shoulder sealing and the installation of curve warning signs with advisory speed plates. From Section 4.3 the following two treatments can be expected to lead to the following crash reduction:

  • Advisory speed signs / Curve warning signs: 15% - 30% reduction
  • Shoulder widening and/or sealing: 30% - 60% reduction

If in this example we used the lower expected crash reduction value of each remedial treatment (i.e. 15% and 30%), and say at this site there were 10 run-off road crashes over a preceding 5-year period, then the combined effect of both treatments would be:

  • Advisory speed signs / Curve warning signs: 15% x 10 crashes = reduction of 1.5 crashes (leaving 8.5 crashes)
  • Shoulder widening and/or sealing: 30% x 8.5 crashes (not 10) = reduction of a further 2.5 crashes (leaving 6 crashes)
  • Total Reduction = 1.5 + 2.5 = 4 crashes from a previous 10 crashes (40% reduction)

Note: Reversing the treatment calculation will not alter the final Total Reduction value.

If in the same example we used the higher expected crash reduction value (i.e. 30% and 60%), thecombined effect of both treatments would be:

  • Advisory speed signs / Curve warning signs: 30% x 10 crashes = reduction of 3 crashes (leaving 7 crashes)
  • Shoulder widening and/or sealing: 60% x 7 crashes (not 10) = reduction of a further 4.2 crashes (leaving 6 crashes)
  • Total Reduction = 3 + 4.2 = 7.2 crashes from a previous 10 crashes (72% reduction)

The expected combined effect of both of these treatments would therefore be a reduction of 40% - 72% in run-off road crashes.

2. Crash data

2.1 Importance and use

Accurate crash data allows:

  • High crash locations (i.e. intersections, routes and lengths, and precincts and local areas) to be accurately identified
  • Crash causation/severity factors to be identified, which then enable target treatment options to be selected
  • The prioritisation of the treatment of high crash locations
  • Crash trends to be plotted and emerging safety issues to be identified
  • Treatments and safety programs to be monitored and evaluated

2.2 Casualty crashes and casualties

Casualty crashes

Casualty crashes are generally categorised as either a fatal crash, a serious injury crash (i.e. hospitalised) or a minor injury crash (i.e. requiring medical attention but not requiring hospitalisation).  In some cases a crash may be categorised as being a serious injury crash, because the injured person was taken away in an ambulance, but in fact the person was taken to hospital as a precaution and in reality the injuries sustained were of a minor nature.

Each crash indicates the highest severity experienced within the collision. For example a fatal crash may have resulted in a number of persons killed and injured.

Casualties

Casualties are the total number of persons killed, seriously injured or who may have suffered minor injuries in a crash or crashes.

2.3 Crash data sources

Generally crash data is collected by the police, who in turn provide it to the state or national road agencies. Hospitals and vehicle injury insurance companies are other sources of crash data. 

 

3. Solutions for different road user safety problems

3.1 Pedestrian crashes

A detailed crash investigation is required to identify crash causation and crash severity factors. This information will form the basis for the selection of the targeted cost-effective remedial treatment options.

The solution selected will ultimately depend upon available budget, prevailing site factors, treatment cost, CRF or CMF and economic worth of the treatment.

The combined effectiveness of multiple remedial treatments is NOT additive. Refer to Section 1.4 for calculating the expected effectiveness of multiple treatments.

Solutions

Tmt Life (years)

Effectiveness

Cost

Pedestrian crossing (un-signalised)

1-5

$

Traffic calming (localised / threshold treatments)

10-20

$

Hatched/painted medians

1-5

$

Pedestrian crossing raised (un-signalised)

5-10

$

Parking improvements[2]

5-10

$

Pedestrian fencing

10-15

$

Kerb extensions

5 - 10

$

Traffic calming (treatments along a road segment)

10-20

$$

Sight distance improvements / remove obstruction

10-15

$$

School zones[3]

5-10

$$

Median – raised / pedestrian refuge

5-10

$$

Skid resistance improvements

5-10

$$

Pedestrian streets in commercial zones

20-30

$$

Speed management/lower speed limits[4]

5-10

$$

Footpaths

10-20

$$$

Street lighting[5]

10-20

$$$

Pedestrian crossing - signalised

10-20

$$$

Intersection signals

10-20

$$$$

Traffic calming (area-wide treatments)

10-20

$$$$

Service roads

20-30

$$$$

Pedestrian overpass

20-30

$$$$

up to 15% reduction     15% to 30% reduction

30% to 60% reduction        greater than 60% reduction

$ less than US$25,000                     $$  US$25,000 to US$50,000

$$$ US$50,000 to US$100,000      $$$$ greater than US$100,000

[2]Examples include parking bans and converting angle parking to parallel parking.

[3]Speed reducing measures in area around schools.

[4]Effectiveness increases substantially with enforcement.

[5]Crash reduction expected during the night-time.

To assist identify the most appropriate cost-effective treatment refer to:

 

3.2 Bicycle crashes

A detailed crash investigation is required to identify crash causation and crash severity factors. This information will form the basis for the selection of the targeted cost-effective remedial treatment options.

The solution selected will ultimately depend upon available budget, prevailing site factors, treatment cost, CRF or CMF and economic worth of the treatment.

The combined effectiveness of multiple remedial treatments is also NOT additive. Refer to Section 1.4 to calculate the expected effectiveness of multiple treatments.

Solutions

Tmt Life (years)

Effectiveness

Cost

Intersection ‘Stop’ control sign from no control

1-5

$

Bicycle lanes

1-5

$

Parking improvements[6]

5-10

$

Traffic calming (treatments along a road segment)

10-20

$$

Sight distance improvements / remove obstruction

10-15

$$

School zones[7]

5-10

$$

Speed management (incl. review of speed limits)

5-10

$$

Delineation[8]

1-5

$$

Street lighting[9]

10-20

$$$

Restrict or combine direct access points

20-30

$$$

Shoulder sealing

10-15

$$$$

Traffic calming (area-wide treatments)

10-20

$$$$

up to 15% reduction     15% to 30% reduction

30% to 60% reduction        greater than 60% reduction

$ less than US$25,000                   $$  US$25,000 to US$50,000

$$$ US$50,000 to US$100,000      $$$$ greater than US$100,000

[6]Examples include parking bans and converting angle parking to parallel parking

[7]Speed reducing measures in area around schools

[8]Combined delineation measures (i.e. edge-lines, centreline, raised reflective pavement markers and delineator posts); instead of being used in isolation provide the benefits(Elvik et al, 2009)

[9]Crash reduction expected during the night-time

To assist identify the most appropriate cost-effective treatment refer to:

 

3.3 Motorcycle crashes

A detailed crash investigation is required to identify crash causation and crash severity factors. This information will form the basis for the selection of the targeted cost-effective remedial treatment options.

The solution selected will ultimately depend upon available budget, prevailing site factors, treatment cost, CRF or CMF and economic worth of the treatment.

The combined effectiveness of multiple remedial treatments is also NOT additive. Refer to Section 1.4 to calculate the expected effectiveness of multiple treatments.

Solutions

Tmt Life (years)

Effectiveness

Cost

Centre of the road turn-lane

1-5

$

Intersection ‘Stop’ control sign from no control

1-5

$

Intersection delineation

1-5

$

Traffic calming (treatments along a road segment)

10-20

$$

Intersection turn-lanes (signalised/un-signalised)

1-5

$$

Sight distance improvements / remove obstruction

10-15

$$

Speed management (incl. review of speed limits)

5-10

$$

Roadside safety –remove hazard

5-10

$$

Delineation[10]

1-5

$$

Skid resistance improvements

5-10

$$$

Motorcycle lanes

10-20

$$$

Road realignment - vertical

20-30

$$$$

Road realignment – horizontal

20-30

$$$$

Additional lane

15-20

$$$$

Road shoulder sealing

10-15

$$$$

Roundabouts

10-20

$$$$

up to 15% reduction     15% to 30% reduction

30% to 60% reduction        greater than 60% reduction

$ less than US$55,000                  $$  US$25,000 to US$50,000

$$$ US$50,000 to US$100,000      $$$$ greater than US$100,000

[10]Combined delineation measures (i.e. edge-lines, centreline, raised reflective pavement markers and delineator posts); instead of being used in isolation provide the benefits(Elvik et al, 2009)

To assist identify the most appropriate cost-effective treatment refer to:

 

3.4 Trucks and buses crashes

A detailed crash investigation is required to identify crash causation and crash severity factors. This information will form the basis for the selection of the targeted cost-effective remedial treatment options.

The solution selected will ultimately depend upon available budget, prevailing site factors, treatment cost, CRF or CMF and economic worth of the treatment.

The combined effectiveness of multiple remedial treatments is also NOT additive. Refer to Section 1.4 to calculate the expected effectiveness of multiple treatments.

Solutions

Tmt Life (years)

Effectiveness

Cost

Centre of the road turn-lane

1-5

$

Intersection ‘Stop’ control sign from no control

1-5

$

Intersection delineation

1-5

$

Intersection turnlanes (sig/un-signalised)

5-10

$$

Sight distance improvements / remove obstruction

10-15

$$

Speed management (incl. review of speed limits)

5-10

$$

Roadside safety – remove hazard

5-10

$$

Delineation[11]

1-5

$$

Median - raised

10-15

$$$

Passing / overtaking lanes (one-direction)

15-20

$$$

Sealing shoulders/widening

5-10

$$$

Traffic lane widening

5-10

$$$

Passing / overtaking lanes

10-15

$$$

Skid resistance improvements

5-10

$$$

Median barriers (rigid)

10-20

$$$$

Intersection signals

10-20

$$$$

Road realignment - vertical

20-30

$$$$

Passing / overtaking lanes (two-directions)

15-20

$$$$

Road realignment – horizontal

20-30

$$$$

Roundabouts

10-20

$$$$

up to 15% reduction     15% to 30% reduction

30% to 60% reduction        greater than 60% reduction

$ less than US$25,000                  $$  US$25,000 to US$50,000

$$$ US$50,000 to US$100,000      $$$$ greater than US$100,000

[11]Combined delineation measures (i.e. edge-lines, centreline, raised reflective pavement markers and delineator posts); instead of being used in isolation provide the benefits(Elvik, R, et al, 2009)

To assist identify the most appropriate cost-effective treatment refer to:

 

4.   Solutions for different types of crashes

4.1 Intersection crashes

A detailed crash investigation is required to identify crash causation and crash severity factors. This information will form the basis for the selection of the targeted cost-effective remedial treatment options.

The solution selected will ultimately depend upon available budget, prevailing site factors, treatment cost, CRF or CMF and economic worth of the treatment.

The combined effectiveness of multiple remedial treatments is also NOT additive. Refer to Section 1.4 to calculate the expected effectiveness of multiple treatments.

Solutions

Tmt Life (years)

Effectiveness

Cost

Intersection ‘Stop’ control sign from no control

1-5

$

Intersection delineation

1-5

$

Sight distance improvements / remove obstruction

10-15

$$

One-way operation

20-30

$$

Parking improvements[12]

5-10

$$

Intersection turn-lanes (sig/un-signalised) painted

1-5

$$

Street lighting (rural)[13]

10-20

$$

Street lighting (urban)[14]

10-20

$$

Speed management (incl. review of speed limits)

5-10

$$

Sealing shoulders/widening

5-10

$$$

Improved skid resistance

5-10

$$$

Intersection turn lanes (sig/un-signalised) built

10-15

$$$

Grade separation from un-signalised intersection

20-30

$$$$

Intersection signals

10-20

$$$$

Roundabout

10-20

$$$$

up to 15% reduction     15% to 30% reduction

30% to 60% reduction        greater than 60% reduction

$ less than US$25,000                  $$  US$25,000 to US$50,000

$$$ US$50,000 to US$100,000      $$$$ greater than US$100,000

 

[12]Examples include parking bans and converting angle parking to parallel parking

[13]Crash reduction expected during the night-time

[14]Crash reduction expected during the night-time

To assist identify the most appropriate cost-effective treatment refer to:

 

4.2 Head-on crashes

A detailed crash investigation is required to identify crash causation and crash severity factors. This information will form the basis for the selection of the targeted cost-effective remedial treatment options.

The solution selected will ultimately depend upon available budget, prevailing site factors, treatment cost, CRF or CMF and economic worth of the treatment.

The combined effectiveness of multiple remedial treatments is also NOT additive. Refer to Section 1.4 to calculate the expected effectiveness of multiple treatments.

Solutions

Tmt Life (years)

Effectiveness

Cost

Centre of the road turn-lane

1-5

$

Intersection delineation

1-5

$

Sight distance improvements

5-10

$

Delineation[15]

1-5

$$

Painted/flush median

1-5

$$

Rumble strip (or milled) centre line

1-5

$$

Traffic calming (treatments along a road segment)

10-20

$$

One-way operation

20-30

$$

Speed management (incl. review of speed limits)

5-10

$$

Additional lane

10-20

$$$

Median - raised

5-10

$$$

Lane widening

5-10

$$$

Road realignment - vertical

20-30

$$$$

Road realignment - horizontal

20-30

$$$$

Shoulder widening and/or sealing

5-10

$$$$

Median barrier - flexible or semi-rigid

5-15

$$$$

Median barrier - rigid

10-20

$$$$

up to 15% reduction     15% to 30% reduction

30% to 60% reduction        greater than 60% reduction

$ less than US$25,000                  $$  US$25,000 to US$50,000

$$$ US$50,000 to US$100,000      $$$$ greater than US$100,000

[15]Combined delineation measures (i.e. edge-lines, centreline, raised reflective pavement markers and delineator posts); instead of being used in isolation provide the benefits (Elvik, R, et al, 2009)

To assist identify the most appropriate cost-effective treatment refer to:

                           

4.3 Run-off-road crashes

A detailed crash investigation is required to identify crash causation and crash severity factors. This information will form the basis for the selection of the targeted cost-effective remedial treatment options.

The solution selected will ultimately depend upon available budget, prevailing site factors, treatment cost, CRF or CMF and economic worth of the treatment.

The combined effectiveness of multiple remedial treatments is also NOT additive. Refer to Section 1.4 to calculate the expected effectiveness of multiple treatments.

Solutions

Tmt Life (years)

Effectiveness

Cost

Install a safety (sealed) edge[16]

20

$

Traffic calming (treatments along a road segment)

10-20

$$

Delineation[17]

1-5

$$

Speed management (incl. review of speed limits)

5-10

$$

Roadside safety – remove hazard

5-10

$$

Roadside barrier

10-15

$$

Improved skid resistance

5-10

$$$

Lane widening

5-10

$$$

Impact attenuation tmt at select roadside hazard[18]

1-5

$$$

Flatten road side slope [19]

20-30

$$$

Road realignment - vertical

20-30

$$$$

Road realignment - horizontal

20-30

$$$$

Shoulder widening and/or sealing

5-10

$$$$

Median barrier - flexible or semi-rigid

10-15

$$$$

Median barrier - rigid

10-20

$$$$

up to 15% reduction     15% to 30% reduction

30% to 60% reduction        greater than 60% reduction

$ less than US$25,000                  $$  US$25,000 to US$50,000

$$$ US$50,000 to US$100,000      $$$$ greater than US$100,000

[16] Pavement edge sloped 30°-35° to minimise edge of seal drop-off and to more safely allow vehicle road re-entry. FHWA, Manual for Selecting Safety Improvements on High Risk Rural Roads – Safety (http://safety.fhwa.dot.gov/hsip/hrrr/manual/sec47.cfm)

[17]Combined delineation measures (i.e. edge-lines, centreline, raised reflective pavement markers and delineator posts); instead of being used in isolation provide the benefits(Elvik, R, et al, 2009)

[18]Used to treat select roadside hazards (e.g. exposed bridge column).FHWA, Manual for Selecting Safety Improvements on High Risk Rural Roads – Safety (http://safety.fhwa.dot.gov/hsip/hrrr/manual/sec47.cfm)

[19]FHWA, Manual for Selecting Safety Improvements on High Risk Rural Roads – Safety (http://safety.fhwa.dot.gov/hsip/hrrr/manual/sec47.cfm)

To assist identify the most appropriate cost-effective treatment refer to:

 

4.4 Rear-end crashes

A detailed crash investigation is required to identify crash causation and crash severity factors. This information will form the basis for the selection of the targeted cost-effective remedial treatment options.

The solution selected will ultimately depend upon available budget, prevailing site factors, treatment cost, CRF or CMF and economic worth of the treatment.

The combined effectiveness of multiple remedial treatments is also NOT additive. Refer to Section 1.4 to calculate the expected effectiveness of multiple treatments.

Solutions

Tmt Life (years)

Effectiveness

Cost

Centre of the road turn-lane

1-5

$

Intersection delineation

1-5

$

Traffic calming (treatments along a road segment)

10-20

$$

Intersection turn lanes (signals/non-sigs) painted

1-5

$$

Parking improvements[20]

5-10

$$

Delineation[21]

1-5

$$

Speed management (incl. review of speed limits)

5-10

$$

One-way operation

20-30

$$

Improved skid resistance

5-10

$$$

Intersection turn lanes (sig/un-signalised) built

10-15

$$$

Additional lane

10-20

$$$

Shoulder sealing

5-10

$$$$

Shoulder sealing

5-10

$$$$

up to 15% reduction     15% to 30% reduction

30% to 60% reduction        greater than 60% reduction

$ less than US$25,000                  $$  US$25,000 to US$50,000

$$$ US$50,000 to US$100,000      $$$$ greater than US$100,000

[20]Examples include parking bans and converting angle parking to parallel parking

[21]Combined delineation measures (i.e. edge-lines, centreline, raised reflective pavement markers and delineator posts); instead of being used in isolation provide the benefits(Elvik, R, et al, 2009)

To assist identify the most appropriate cost-effective treatment refer to:

 

4.5 Lane-change / manoeuvring crashes

A detailed crash investigation is required to identify crash causation and crash severity factors. This information will form the basis for the selection of the targeted cost-effective remedial treatment options.

The solution selected will ultimately depend upon available budget, prevailing site factors, treatment cost, CRF or CMF and economic worth of the treatment.

The combined effectiveness of multiple remedial treatments is also NOT additive. Refer to Section 1.4 to calculate the expected effectiveness of multiple treatments.

Solutions

Tmt Life (years)

Effectiveness

Cost

Centre of the road turn-lane

1-5

$

Intersection delineation

1-5

$

Parking improvements[22]

 

$

Traffic calming (treatments along a road segment)

10-20

$$

Intersection turn lanes (signals/non-sigs) painted

1-5

$$

Delineation[23]

1-5

$$

Speed management (incl. review of speed limits)

5-10

$$

Intersection turn lanes (sig/un-signalised) built

10-15

$$$

up to 15% reduction     15% to 30% reduction

30% to 60% reduction        greater than 60% reduction

$ less than US$25,000                   $$  US$25,000 to US$50,000

$$$ US$50,000 to US$100,000      $$$$ greater than US$100,000

[22]Examples include parking bans and converting angle parking to parallel parking

[23]Combined delineation measures (i.e. edge-lines, centreline, raised reflective pavement markers and delineator posts); instead of being used in isolation provide the benefits(Elvik, R, et al, 2009)

To assist identify the most appropriate cost-effective treatment refer to:

 

 

5.   Monitoring and evaluation - is it the solution working?

Monitoring is the systematic collection and assessment of data immediately after treatment implementation, while evaluation is the statistical analysis of before and after crash and/or speed data. In each case, the tasks seek to determine the impact of the treatment and are crucial in the effective treatment of crash locations

It enables road safety practitioners to determine the degree to which remedial measures were effective in reducing the incidence and severity of crashes.

It also provides the opportunity to identify unintended or adverse consequences early during the monitoring phase to be identified and corrected.

6.   References

Elvik, R, Hoyes, A, Vaa, T, and Sorensen, M(2009).The Handbook of Road Safety Measures 2nd Ed. UK.

FHWA, Manual for Selecting Safety Improvements on High Risk Rural Roads – Safety (http://safety.fhwa.dot.gov/hsip/hrrr/manual/sec47.cfm).

Global Road Safety Partnership (2008). , Speed Management: a Road Safety Manual for Decision-makers and Practitioners.

PIARC forthcoming 2015.Road Safety Manual.

WHO (2013). Pedestrian safety: a road safety manual for decision-makers and Practitioners.

http://toolkit.irap.org/