Roadworks and Road Safety
In the City of Johannesburg, it was found that the level of obedience to speed limits in road works was much lower than elsewhere and that the attitude of some motorists was alarming.
Drivers are at risk in road works where the lanes may be narrower, the layouts change and there is no hard shoulder for broken down vehicles. This was confirmed by Mr Nick Stroebel, Site SHE Manager at the road works stating that due to the fact that widening has occurred it means that the original lanes have been reduced from 3.7m to 3.3m per lane.
Just because there may not be road workers present it doesn't mean that the motoring public is not at risk from the unexpected.
Temporary speed signs at road works are not suggested speeds - they are the legal limit while the signs are displayed. Workers and motorcyclists are particularly at risk from flying stones and loose surfaces. Loss-of-control accidents are much more likely. One small mistake could easily cost a workman his life.
Additionally, road works present a clear danger to motorists and road workers alike - a danger often forgotten. Despite all the measures undertaken to maintain safety, approximately 22% of motorway accidents occur at road works. In addition road, works are estimated to cause up to 15% of network congestion and are regularly subject to public complaints.
Speed enforcement by the camera has shown a decrease of 55% in the accidents that happened in the construction area, between Maraisburg Road overhead bridge and the Soweto High Way for the period of April 2009 compared to March 2009.
Why is speed reduced?
- Speeding vehicles are a very real threat to the safety of other drivers and road workers.
- The road condition may have changed but you may not be aware of this. While under construction or repair, the road surface may not be safe to drive on at the normal speed.
- Loose gravel on the road surface may cause damage to your vehicle.
- The pavement surface may be uneven.
- The road lanes may have narrowed.
- Kilometres of utilities such as drainage pipes, electrical and telecommunication lines are often hidden from view. When roads are widened, many of these have to be relocated. Relocation takes time.
- Some roadwork activities are mobile, such as line markings, road patching and mowing. The road worker may be moving through the zone and needs a reduced speed limit for safety reasons.
- Road workers may not always be visible when working in the road area.
Roadwork activities can cause dangerous situations for both road users and road workers.
- In 2005, 2% of all serious, registered crashes in the Netherlands happened during road works.
- In addition, road works seem to increase the crash rate.
- National trunk roads count relatively many fatalities during road works, and heavy vehicles are relatively often involved in these crashes.
- A number of urban crashes were caused by slow traffic entering a closed off road.
- Crashes on rural roads relatively often are rear-ended collisions,
- and some crashes involve work vehicles, impact attenuators and other objects.
- Speeding is a primary cause of these crashes.
Speed reduction measures like
- dynamic speed information, and
- credible limits
can help to reduce speeds at road works. Impact attenuators lower the risk and reduce the severity of road works crashes.
Roadwork activities can consist of
- reconstruction or
- new construction (alongside an existing road, like for instance the construction of extra lanes).
Most maintenance work recurs annually, e.g. maintenance of trees and other plants, and sweeping the emergency lanes and drainage gutters.
Roadwork activities can also consist of installing detection loops, and the maintenance of signposting and constructions. In addition, large-scale maintenance occurs approximately every fifteen years, such as renewal of the road surface (re-tarring) or replacement of guardrails.
Roadwork activities on or alongside a road cause
- a discontinuity in the road layout. During road works
- the expectations of the road user are disturbed and
- their driving behaviour is influenced.
This can result in
- unsafe situations for road users as well as for road workers.
- It can also hinder the traffic flow.
Therefore, measures and facilities are necessary during road works to limit the negative effects on road safety and traffic flow.
At which locations and under what circumstances do road works crashes happen?
- The work zone appears to be the riskiest area at road works.
- In rural areas, road works crashes often occur in the vicinity of slip roads.
- Road workers experience working at night as being dangerous (Swuste & Heijer, 1999). Literature indeed shows that at road works the night hours generally have an increased crash rate (Van Gent, 2007). The number of road works crashes, however, is higher during the day: more than two-thirds of the road work crashes happen in the daytime and the proportion of nightly road works crashes is barely higher than that of daytime crashes. This is probably due to the fact that road works are more frequently carried out during the day, rather than at night. More than two-thirds of the road work crashes happen in dry weather and on a dry road surface.
Who are involved in road works crashes?
In by far, the most road works crashes only road users are involved. Crashes involving road workers form only a small part of all road works crashes (Hagenzieker, 1998).
Although the number of casualties among road workers is limited, there are more work hazards for road workers than for industrial workers (Swuste & Heijer, 1999). Venema et al. (2008) also conclude that the risk of a fatal accident is probably higher for road workers than for the building trade in general. It has also been shown that half the road workers always or often feel unsafe during their working hours.
A crash analysis using BRON data shows that freight traffic is relatively often involved in road works crashes. Overall, a freight vehicle is involved in 6% of the crashes; this is 14% for road works crashes. Other studies confirm this picture (Van Gent, 2007).
What are the causes of road works crashes?
The international literature shows that road works crashes were relatively often rear-ended crashes (Van Gent, 2007). Recent Dutch crash data confirm this: 31% of all rural road works crashes are rear-ended crashes, in comparison with 15% of all rural crashes.
Short headway distances and speeding play an important role in the occurrence of rear-end crashes.
An extensive literature study of road user behaviour in the vicinity of road works was carried out in the European ARROWS project (ARROWS, 1999). The European PREVENT project has summarised the main findings and has studied more recent literature (PREVENT, 2003).
The most consistent finding is that:
- speeding is common at road works.
- The majority of drivers drive too fast when approaching roadworks.
- Drivers often do not reduce their speed until the traffic situation immediately in front of them urges them to do so (just before an abrupt change of circumstances) and consequently brake too hard.
- Although 'fast' drivers (with a high initial speed) have a relatively larger speed reduction than 'slow' drivers, their end speed still is higher.
- In addition, changing lanes is left rather late when a lane is closed off (Schuurman, 1991).
In a number of urban crashes, especially slow traffic enters a blocked road and then collides with works traffic, falls, or rides into a ditch (Janssen & Weijermars, to be published). Lack of clarity about the diversion and the lack of distinct marking of the work area seem to contribute to these crashes occurring.
Which measures can be taken?
- Reducing the maximum speed is intended to ease the driving task.
- In addition, it also reduces the risk of a crash and
- lessens its severity.
Supplementary measures like enforcement and dynamic speed information can be used to actually exact compliance.
Dynamic speed information is a measure which is used to measure the actual speed of each individual vehicle and communicate it to the driver (feedback). Research has shown that this causes drivers to lower their speed (Geluk et al., 2003).
In 2006, the Ministry of Transport started a new trial to reduce speed at road works. Road users were given immediate feedback on their speed, and at the same time, their vehicle registration number was shown. This direct feedback seemed to have speed reduction as a result (AVV, 2007).
The lower a speed limit is, the more it is exceeded. A speed limit seems to be more acceptable and complied with when it is credible. Therefore, in 2005 the Dutch Ministry of Transport introduced new speed regulations during roadworks on motorways. The maximum speed is now 90 km/h and this is only lowered to 70 km/h if the lanes are narrow or if road workers work right next to the lanes without any barriers. When signalling is present on the road, speeds can be differentiated between lanes or for the time of day.
Impact attenuators reduce the risk of crashes and in addition lessen their severity. Barriers lower the risk of a road user driving into the work area, but they increase the possibility of a crash with a rebounding vehicle. Physical barriers must therefore only be placed if they are absolutely necessary (Van Gent, 2007).
Every year, an average of 193 serious injury crashes of which 21 are fatal to occur at road works locations in the Netherlands.
- Most crashes occur during work on the roadway and the work area has the highest risk.
- Road works of a longer duration and covering a longer distance seem to have a lower crash rate.
- Relatively many road works crashes occur on national trunk roads and trucks are relatively frequently involved in road works crashes.
- Furthermore, the literature shows a generally higher crash rate during the night hours.
- Especially on rural roads many of the road works crashes are rear-end crashes.
- There are also crashes involving vehicle-mounted arrow boards and barriers.
- Speeding plays a significant role in this type of crash.
- A literature study into road user behaviour at road works locations shows that speeding is frequent.
Speed measures like enforcement and dynamic speed information (feedback) can help to reduce speeds at road works. In addition, the Dutch Ministry of Transport has introduced new, more credible speed limits for roadworks on motorways. The speed limit can also be differentiated across the lanes or for the time of day. Impact attenuators reduce the risk of road works crashes and their severity.
The work area must be indicated and the traffic must be guided clearly and unambiguously so that the road user is informed about the road works in time and knows what he is expected to do. There also must be sufficient space or barriers between road workers and traffic.
In order to provide safety for workers and road users, it is essential that motorists comply with the speed requirements for road works site.
Without enforcement, it is likely that some motorists will not comply with the speed limits. There is a link between the level of enforcement and the level of compliance so it is necessary to enforce at a level which will result in the majority of motorists obeying the speed limits.
The deterrent provided by enforcement is key to achieving the compliance needed on a roadworks site.
The provision of speed cameras has proven an effective tool for reducing speed at road works.
The use of temporary speed cameras should be seriously considered at road work sites on the strategic road network.
Johansson P. 1996. Speed limitation and motorway casualties: a time series count data regression approached. Accident Analysis and Prevention.
Joksch HC. An empirical relation between fatal accident involvement per accident involvement and speed.
Moore VM, Dolinis J, Woodward AJ. Vehicle speed and risk of a severe crash. Epidemiology
Munden JM. The relationship between a driver’s speed and his accident rate. Berkshire: Transport and Research Laboratory.
Cameron, M.H., Cavallo, A., & Gilbert, A.(1992). Crash-based evaluation of the speed camera program in Victoria 1990-1991. Phase 1: general effects. Phase 2: effects of program mechanisms. Monash University Accident Research Centre, Report Number 42. Clayton, Victoria.
Corbett, C. (1995). Road traffic offending and the introduction of speed cameras in England: The first self-report survey. Accident Analysis and Prevention, 27(3), 345-354.
Elvik, R. (1997). Effects on accidents of automatic speed enforcement in Norway. Transportation Research Record, 1595, 14-19.
Keall, M. D., Povey, L. J. & Frith, W. J., (2002). Further, results from a trial comparing a hidden speed camera program with visible camera operation. Accident Analysis and Prevention, 34, 773-777.
Kloeden, C.N., McLean, A.J., Moore, V.M. & Ponte, G. (1997). Travelling speed and the risk of crash involvement. NHRMC Road Accident Research Unit, University of Adelaide.
Kloeden, C.N., Ponte, G. & McLean, A.J. (2001). Travelling speed and the risk of crash involvement on rural roads. Road Safety Report CR204, Australian Transport Safety Bureau.
LTSA (2002). Public attitudes to road safety, highlights of the 2002 survey. Land Transport Safety Authority, www.ltsa.govt.nz .
Mara, M.K., Davies, R.B. & Frith, W.J. (1996). Evaluation of the effect of compulsory breath testing and speed cameras in New Zealand. Proceedings Combined 18th ARRB Transport Research Conference and Transit NZ Land Transport Symposium, Christchurch, NZ.
Newstead, S.V., Mullan, N.G. and Cameron, M.H. (1995). Evaluation of the speed camera program in Victoria 1990-1993. Phase 5: Further investigation of localised effects on casualty crash frequency. Report 78, Monash University Accident Research Centre.
Nilsson, G. (1982). The effects of speed limit on traffic accidents in Sweden. VTI Sartryck, 68, 1-10.
Redelheimer, Donald A., Tibshirani, Robert J., and Evans, Leonard (2003). Traffic-law enforcement and risk of death from motor-vehicle crashes: a case-crossover study. Lancet, 28 June 2003, 361: 2177-2182.
SAS Institute (1996). SAS/Stat software changes and enhancements through release 6.11.
Zaal , D. (1994). Traffic law enforcement: A review of the literature. Monash University
Accident Research Centre, report No 53. Prepared for Federal Office of Road Safety, Canberra and Institute for Road Safety Research (SWOV), The Netherlands.
Accident Reconstructionist for the RAF
Manager: Accident Analysis Division
TMT Services and Supplies PTY Ltd