Road safety at intersections
Due to crossing traffic and the often high-speed, side-impact of a potential crash, intersections are very risky locations from a road safety perspective. In the US quarter of all crash victims (*1) occur at intersections. In the Netherlands this is roughly one third (*2), mainly due to the high percentage of Vulnerable Road Users (VRU). Of the total number of cyclists killed in the Netherlands 54% are killed at intersections.
These figures are even more remarkable if you consider the fact that intersections take up a relatively small part of the total road length traveled. It pays to address road safety at intersections and explains why it is effective to convert intersections into roundabouts. However, such changes are expensive and often not feasible due to space constraints, existing buildings and land ownership. Roundabouts take more space than traditional intersections. Improved road safety is caused by the fact that roundabouts force vehicles to slow down and change the potential crash impact angle. Both these factors reduce the risk of serious crashes. A comprehensive review of non-US studies found that roundabouts are associated with a 30% to 50% reduction in the number of injury accidents, and a 50% to 70% reduction in fatal accidents (*3).

Two roundabouts with separate and integrated cycle tracks in the Netherlands (Source: Voorrang en Rotondes 13-1757 - ROVL Limburg).

Almost three quarters of intersection crashes (*2) occur in urban areas. However, in rural areas and other roads where vehicle speeds are higher, the consequences of intersection crashes can be extremely severe. Chances of serious injury or death increase dramatically with vehicle speeds above 30 km/h. This applies in particular to vulnerable road users.

The IRAP Road Safety Tool Kit (*4) reports various intersection crash types, including:
– Collision between oncoming vehicles, particularly when turning across traffic
– Right-angle collisions, where neither vehicle is turning (often at high speed)
– Right-angle or side-swipe collisions where one or more vehicles are turning
– Rear-end crashes

IRAP specifies the following causes of intersection crashes:
– Inadequate sight distance to on-coming vehicle
– High approach speeds
– Lack of intersection visibility (road users aware of upcoming intersection)
– Lack of gaps in traffic
– Complex intersection layout
– Poor road surface condition

It makes sense to specifically focus on an integral approach to intersection safety as part of a balanced road safety strategy. Besides roundabouts, intersection safety can be improved by traffic and warning lights, signage, speed humps, plateaus and rumble strips. Most of these measures focus on lowering speeds, regulating traffic, improved overview and better visibility and increasing attention levels.

Red-light cameras (RLCs) are also a frequent safety measure used at high risk signalised intersections. RLCs are less controversial than speed cameras since almost everyone agrees that red-light violations are extremely dangerous. Many drivers do not see such risks with limited speeding. In many countries red-light cameras are equipped with integrated speed cameras. This means speeding up in order to ‘just make it’ through a green or yellow light will also be punished. Depending on the jurisdiction, speeding and ignoring a red light simultaneously, could result in a double fine. On the other hand, many drivers claim that red-light cameras are bad for road safety. They believe that they actually increase the number of intersection crashes. Is this claim true?

Red-light and speed enforced intersection in Qatar.

A wide range of studies were conducted to evaluate the merits of RLCs. Summaries of these studies are listed below. The links to the full content studies are listed under sources at the bottom of this article.

The Insurance Institute of Highway Safety (IIHS) (*5) reports that camera enforcement programs were associated with a statistically significant reduction in the city-wide rate of fatal red light running crashes, and also with a smaller but still significant reduction in the rate of all fatal crashes at signalized intersections. RLC programs in 79 large U.S. cities saved nearly 1,300 lives through 2014, researchers from the Insurance Institute for Highway Safety have found. Shutting down such programs costs lives. The rate of fatal red-light-running crashes shot up 30 percent in cities that turned off RLCs.

A Federal Highway Administration (FHWA) study on the impact of RLCs (*6) concludes: this economic analysis represents the first attempt in the known literature to combine the positive effects of right-angle crash reductions with the negative effects of rear end crash increases and identify factors that might further enhance the effects of RLC systems. The following primary conclusions are based on these current analyses: Even though the positive effects on angle crashes of RLC systems is partially offset by negative effects related to increases in rear end crashes, there is still a modest to moderate economic benefit of between $39,000 and $50,000 per treated site year. Even if modest, this economic benefit is important. In many instances today, the RLC systems pay for themselves through red-light-running fines generated. However, in many jurisdictions, this differs from most safety treatments where there are installation, maintenance, and other costs that must be weighed against the treatment benefits. The modest benefit per site is an average over all sites. As the analysis of factors showed, this benefit can be increased through careful selection of the sites (e.g., sites with a high ratio of right-angle to rear end crashes as compared to other potential treatment sites) and program design (e.g. high publicity).

Researchers from SWOV, the Dutch Road Safety Research Institute, co-authored a paper in the magazine 'Accident Analysis & Prevention' (*7). The aim of this paper is to update the most recent published evidence on road safety estimates of recent RLC and speed/red light camera studies (SRLC).

A literature search was carried out on RLC studies in the period 2013-2017 which, after screening, identified 18 recent studies on red light cameras (RLCs) and speed/red light cameras (SRLCs). The methodology and results of these studies were further examined and summary safety estimates were derived and compared to earlier meta-analysis summary estimates.

The primary conclusion is that the new safety estimates from this paper show a 12% decrease of total crashes and confirm the general tendency of RLCs to reduce right angle crashes while at the same time increasing rear end crashes. However, comparing the developments over time, the review reveals that safety estimates tend to increase with time (the safety effects of the most recent studies are the greatest). Also safety estimates suggest more positive effects with SRLCs than with RLCs. Most recent studies indicate that spillover effects are present and can be quite substantial.

Red-light and speed enforced intersection in the Netherlands.

The Monash University Accident Research Centre (*8) studied the effects of red-light cameras at 77 intersections in Victoria, Australia. It was estimated that 17 serious or fatal crashes per year and 39 minor injury crashes were to be prevented at these intersections. This represented crash cost savings to the community of roughly AUD 8M or EUR 5.2M. When only the crashes involving vehicles travelling from the approach intersection leg where the camera was placed are considered, the estimated casualty crash reduction was 47%. When crashes involving vehicles from all approaches are compared, the estimated casualty crash reduction was 26%. They also calculated a 44% reduction in right angle and right turn against crashes. This type of collision is targeted in particular by red light enforcement.

In this study a combination of speed and red-light enforcement in one fixed camera system was used. This was rather unique and had not been previously evaluated. Based on the outcomes of this evaluation, continued and expanded use of combined fixed red-light and speed cameras in Victoria is expected to improve driver safety, save lives and reduce crash related costs.

On the basis of 10 controlled before-after studies from Australia, Singapore and the USA, a Cochrane Library report (*9) concluded that red-light cameras are effective in reducing total casualty crashes. However, the evidence is less conclusive on total collisions, specific casualty collision types and violations. Some reductions achieved could be explained by the play of chance. Most evaluations did not adjust for regression to the mean (RTM) or spill over, affecting their accuracy.

A study in the magazine Traffic Injury Prevention (*10) reviewed and evaluated available evidence in the international literature regarding the effectiveness of cameras to reduce both red light violations and crashes. Camera enforcement generally reduces violations by an estimated 40-50%. In terms of crash effects, most studies contain methodological flaws that, to varying degrees, either overestimate (failure to adjust for regression to the mean) or underestimate (comparison with nearby signalised intersections affected by cameras) crash effects. Mindful of these limitations, the research generally indicates that camera enforcement can significantly reduce injury crashes at signalised intersections. This applies in particular to right-angle injury crashes. Most studies reported increases in rear-end crashes following camera installation. Taken together the studies indicate that, overall, injury crashes, including rear-end collisions, were reduced by 25-30% as a result of red-light camera enforcement.

Red-light camera in the UK.

The TTI study (*11), although limited to Texas, is one of the most extensive in the nation and focused on the safety aspects of red-light camera use. The primary objective of the study, sponsored by the Texas Department of Transportation, was to evaluate the effectiveness of automated traffic enforcement systems in reducing right-angle, rear-end and other crash types at signal-controlled intersections across the state, and to report the findings surrounding crash incidence at those intersections.

Researchers examined more than 11,000 records of crashes occurring at the 275 intersections statewide where cameras were in place, and compared crash frequencies one, two and three years before and after installation of the cameras.

An overall reduction of 633 crashes recorded at those intersections represents an 11 percent decline. Red-light-related crashes dropped by 25 percent, and right-angle crashes (the most severe type) dropped by 32 percent. The reductions were seen across the board on all types of roadways, including business/primary roads, farm-to-market roads, interstate access roads, state highways and U.S. highways.

Researchers also compared crash frequencies at different intervals before and after cameras were installed. The examination showed a 23 percent drop from one year before to one year after cameras were put into use. The two- and three-year comparisons reflected reductions of 27 percent and 21 percent, respectively.

The TTI research comes soon after another study showing that a majority of drivers support the use of the cameras. Focusing on 14 cities in nine states that had red-light camera programs in place, the IIHS found that two-thirds of drivers favoured the cameras, and 59 percent believed that the cameras had made intersections safer.

According to the National Highway Traffic Safety Administration, red-light running causes more than 100,000 crashes and nearly 1,000 fatalities every year, and right-angle crashes account for 46 percent of all intersection-related collisions.

Red-light camera in Dubai.

Several pro-motorist sites claim red-light cameras are dangerous (*12, 13) and that they actually increase the number of crashes. Moreover, for the United States these sites claim that enforcement cameras are used to fill government coffers through fine collection and that their road safety benefits are very limited. Some red-light effect studies indeed indicate that there may be slightly more rear-end collisions with the use of red-light cameras. However, this pales compared to the reduction in the number of right-angle and other high impact crashes that tend to cause considerably more casualties and severe injuries.

It is important to look at each road crossing separately and look at a wide range of potential intersection safety measures. Special attention should be given to vulnerable road users, since they run the highest risk at intersections, especially with red-light running by cars and other heavy vehicles. Red light running may also be caused by a speeding problem at a given crossing.

Signage indicating red-light and speed cameras in Australia.

It is obvious that improving road safety at signalised intersections by only installing red light cameras with or without integrated full-time speed enforcement has limited effect. Comprehensive road safety planning at intersections should also consider infrastructure measures (e.g. roundabouts, speed humps, rumble strips, plateaus, mirrors) possibly in combination with signage (signs, flashing lights, count-down timers), speed management and publicity.

Arguments that red-light cameras cause more crashes and are thus counterproductive to road safety are not supported by academic research and can be considered as ‘fake news’.

*1) Insurance Institute of Highway Safety: http://www.iihs.org/iihs/topics/t/roadway-and-environment/fatalityfacts/roadway-and-environment - (2022)

*2) SWOV, Netherlands Road Safety Research Institute: https://www.swov.nl/feiten-cijfers/factsheet/kruispunttypen - (2022)

*3) Effects on Road Safety of Converting Intersections to Roundabouts: Review of Evidence from Non-U.S. Studies (Journal of the Transportation Research Board) - Rune Elvik (2003)

*4) International Road Assessment Programme: http://toolkit.irap.org/default.asp?

*5) Insurance Institute of Highway Safety: http://www.iihs.org/iihs/news/desktopnews/turning-off-red-light-cameras-costs-lives-new-research-shows
https://www.iihs.org/topics/red-light-running#effectiveness-of-cameras

*6) Federal Highway Administration: https://www.fhwa.dot.gov/publications/research/safety/05049/

*7) SWOV, Netherlands Road Safety Research Institute: https://swov.nl/en/nieuws/red-light-cameras-revisited-recent-evidence-red-light-camera-safety-effects

*8) Monash University Accident Research Centre: http://www.monash.edu.au/miri/research/reports/muarc307.pdf

*9) Cochrane Library: Red‐light cameras for the prevention of road traffic crashes - Aeron‐Thomas, A - 2005 | Cochrane Library

*10) Traffic Injury Prevention: http://www.tandfonline.com/doi/abs/10.1080/15389580309858

*11) Texas A&M Transportation Institute - https://tti.tamu.edu/researcher/tti-study-underscores-safety-benefits-of-red-light-cameras/

*12) The News Wheel: http://thenewswheel.com/dangerous-effects-do-red-light-cameras-cause-traffic-accidents/

*13) National Motorists Association: https://www.motorists.org/blog/red-light-cameras-increase-accidents-5-studies-that-prove-it/

Written by Philip J. Wijers, Director Government Affairs, Sensys Gatso Group