Speeding in highway work zone: An Evaluation of methods of speed control

Effectiveness of road safety interventions: An evidence and gap map

Background

Road Traffic injuries (RTI) are among the top ten leading causes of death in the world resulting in 1.35 million deaths every year, about 93% of which occur in low- and middle-income countries (LMICs). Despite several global resolutions to reduce traffic injuries, they have continued to grow in many countries. Many high-income countries have successfully reduced RTI by using a public health approach and implementing evidence-based interventions. As many LMICs develop their highway infrastructure, adopting a similar scientific approach towards road safety is crucial. The evidence also needs to be evaluated to assess external validity because measures that have worked in high-income countries may not translate equally well to other contexts. An evidence gap map for RTI is the first step towards understanding what evidence is available, from where, and the key gaps in knowledge.

Objectives

The objective of this evidence gap map (EGM) is to identify existing evidence from all effectiveness studies and systematic reviews related to road safety interventions. In addition, the EGM identifies gaps in evidence where new primary studies and systematic reviews could add value. This will help direct future research and discussions based on systematic evidence towards the approaches and interventions which are most effective in the road safety sector. This could enable the generation of evidence for informing policy at global, regional or national levels.

Search Methods

The EGM includes systematic reviews and impact evaluations assessing the effect of interventions for RTI reported in academic databases, organization websites, and grey literature sources. The studies were searched up to December 2019.

Selection Criteria

The interventions were divided into five broad categories: (a) human factors (e.g., enforcement or road user education), (b) road design, infrastructure and traffic control, (c) legal and institutional framework, (d) post-crash pre-hospital care, and (e) vehicle factors (except car design for occupant protection) and protective devices. Included studies reported two primary outcomes: fatal crashes and non-fatal injury crashes; and four intermediate outcomes: change in use of seat belts, change in use of helmets, change in speed, and change in alcohol/drug use. Studies were excluded if they did not report injury or fatality as one of the outcomes.

Data Collection and Analysis

The EGM is presented in the form of a matrix with two primary dimensions: interventions (rows) and outcomes (columns). Additional dimensions are country income groups, region, quality level for systematic reviews, type of study design used (e.g., case-control), type of road user studied (e.g., pedestrian, cyclists), age groups, and road type. The EGM is available online where the matrix of interventions and outcomes can be filtered by one or more dimensions. The webpage includes a bibliography of the selected studies and titles and abstracts available for preview. Quality appraisal for systematic reviews was conducted using a critical appraisal tool for systematic reviews, AMSTAR 2.

Main Results

The EGM identified 1859 studies of which 322 were systematic reviews, 7 were protocol studies and 1530 were impact evaluations. Some studies included more than one intervention, outcome, study method, or study region. The studies were distributed among intervention categories as: human factors (n = 771), road design, infrastructure and traffic control (n = 661), legal and institutional framework (n = 424), post-crash pre-hospital care (n = 118) and vehicle factors and protective devices (n = 111). Fatal crashes as outcomes were reported in 1414 records and non-fatal injury crashes in 1252 records. Among the four intermediate outcomes, speed was most commonly reported (n = 298) followed by alcohol (n = 206), use of seatbelts (n = 167), and use of helmets (n = 66). Ninety-six percent of the studies were reported from high-income countries (HIC), 4.5% from upper-middle-income countries, and only 1.4% from lower-middle and low-income countries. There were 25 systematic reviews of high quality, 4 of moderate quality, and 293 of low quality.

Authors' Conclusions

The EGM shows that the distribution of available road safety evidence is skewed across the world. A vast majority of the literature is from HICs. In contrast, only a small fraction of the literature reports on the many LMICs that are fast expanding their road infrastructure, experiencing rapid changes in traffic patterns, and witnessing growth in road injuries. This bias in literature explains why many interventions that are of high importance in the context of LMICs remain poorly studied. Besides, many interventions that have been tested only in HICs may not work equally effectively in LMICs. Another important finding was that a large majority of systematic reviews are of low quality. The scarcity of evidence on many important interventions and lack of good quality evidence-synthesis have significant implications for future road safety research and practice in LMICs. The EGM presented here will help identify priority areas for researchers, while directing practitioners and policy makers towards proven interventions.

Evaluation of a Road Safety Awareness Campaign Deployed along the Roadside in Saguenay (Québec, Canada)

For the past few years, police officers from the City of Saguenay have been installing a billboard combined with a damaged car along roadsides to make drivers aware of the road risks related to dangerous behaviors at the wheel. To assess the short-term effect of this device, evaluative research with a quasi-experimental design with pre-exposure, during, and post-exposure. The results show a significant decrease (p < 0.001) of 0.637 km/h for the first site (a 70 km/h zone) and 0.269 km/h for the second site (a 50 km/h zone) when the device is exposed. At the time of this last evaluation, a reduction of 1.255 km/h remained even after the advertising panel was removed. Although minimal, this speed reduction where the billboards are placed shows the police that this awareness-raising approach works since it reduces the speed of motorists at very low cost.

Using Connected Vehicle Trajectory Data to Evaluate the Impact of Automated Work Zone Speed Enforcement

Work zone safety is a high priority for transportation agencies across the United States. Enforcing speed compliance in work zones is an important factor for reducing the frequency and severity of crashes. This paper uses connected vehicle trajectory data to evaluate the impact of automated work zone speed enforcement on three work zones in Pennsylvania and two work zones in Indiana. Analysis was conducted on more than 300 million datapoints from over 71 billion records between April and August 2021. Speed distribution and speed compliance studies with and without automated enforcement were conducted along every tenth of a mile, and the results found that overall speed compliance inside the work zones increased with the presence of enforcement. In the three Pennsylvania work zones analyzed, the proportions of vehicles travelling within the allowable 11 mph tolerance were 63%, 75% and 84%. In contrast, in Indiana, a state with no automated enforcement, the proportions of vehicles travelling within the same 11 mph tolerance were found to be 25% and 50%. Shorter work zones (less than 3 miles) were associated with better compliance than longer work zones. Spatial analysis also found that speeds rebounded within 1–2 miles after leaving the enforcement location.

Improved traffic safety at work zones through animation-based variable message signs

Work zones are established to provide a safe environment for all road users and road workers. However, based on the statistics, they can be considered as crash prone zones due to changes in the road alignments and the posted speed limits. In this driving simulator study, we aimed at investigating the safety impacts of a newly proposed system composed of graphical and animation-based variable message signs (VMSs) in the state of Qatar. The proposed VMS condition was compared with a control condition that was designed following the Qatar Work Zone Traffic Management Guide. A total of seventy subjects were invited to participate in the experiment voluntarily. Study results showed that in the VMS condition, drivers reduced their traveling speeds in advanced compared to the control condition. Drivers' traveling speed in the VMS condition was significantly reduced by 6.3 and 11.1 km/h on the leftmost and the second leftmost lanes, respectively. Next, the results uncovered that the proposed system motivated drivers to initiate early lane changing maneuvers, i.e., 150 m earlier than the control condition. Finally, the VMS condition was effective in stimulating drivers to keep larger headways with a merging vehicle. In sum, the proposed VMS system outperformed the control condition in terms of speed reduction, early merging, and higher headways between the through and the merging vehicle.

Risk to workers or vehicle damage: What makes drivers slow down in work zones?

OBJECTIVE

Speeding in work zones is common and poses significant safety hazards to motorists and workers. Previous studies have demonstrated that speeding is reduced when workers are visible to the drivers, suggesting that concern for the safety of workers influences drivers' speed choice. Conversely, the extent of speeding when workers are not visible suggests that drivers underestimate the increased risk of crashes or other damage to their vehicles associated with the poorer road conditions common at roadworks (loose surfaces and debris, narrower lane width and drop-offs etc.). To better understand the factors influencing drivers' speeds in work zones, this paper examined the extent to which drivers' speed choices are influenced by their perceived likelihoods of injuring workers and damaging their own vehicles.

METHODS

Driver-nominated speeds and perceived likelihoods of worker injury and vehicle damage were collected in an online survey of 405 drivers from Queensland, Australia, by showing photographs of 12 real-world work zones. The data were analyzed using regression techniques to examine the factors influencing driver-nominated speeds and likelihood of speeding.

RESULTS

The results supported the hypothesis that both drivers' perceived likelihood of injuring workers and damaging vehicles strongly influence their nominated speeds (p < 0.001). Young and middle-aged drivers nominated 2.5-6.3 km/h higher speeds than older drivers (p < 0.001). Car drivers who also held truck licenses nominated 4.5 km/h higher speeds (p < 0.001) and 81% higher odds of nominating speeds higher than posted limits (p < 0.001) than car-only licensed drivers. Drivers nominated lower speeds at road curves (12.1 km/h lower speed and 53% lower odds of speeding, p < 0.001), if adjacent areas of travel lanes were unpaved or had loose materials (11.5 km/h lower speed and 66% lower odds, p < 0.001), and when workers were visible in work zones (1.4 km/h lower speed, p = 0.004, and 27% lower odds, p = 0.041).

CONCLUSIONS

In addition to driver demographic and work zone characteristics, drivers' perceptions of safe speeds depend on their perceptions of the likelihood of worker injury and vehicle damage at work zones. These findings suggest that interventions to heighten drivers' perceptions of the likelihood of damage to their vehicles may be useful in moderating speeds at roadworks.

An observational study of skier compliance with posted "slow" signs and ski patrollers

OBJECTIVES

To examine the efficacy of "slow" signs and patroller presence at "slow" signs to reduce speeds of snowsports participants, compared to a condition where no sign or patroller are present, independent of other factors that may contribute to skier slowing (such as prior knowledge, trail convergence, etc.).

DESIGN AND METHODS

Snowsports participant speeds were measured on "more difficult" trails using a radar gun at two ski areas with: (1) no-sign - the usual condition for the trail, and (2) slow-sign - a large "slow" sign was posted in the middle of the trail. At one ski area, a third condition was also tested: (3) slow+patroller - a ski patroller stood at the slow sign. Participant equipment type and estimated ability were also recorded.

RESULTS

At one ski area, there was no significant difference in speed between conditions. At the second ski area, the differences in mean (SD) speeds were small but significant for the no-sign, slow-sign, and slow+patroller conditions: 10.9 (3.0), 10.3 (2.9), and 9.8 (2.6)m/s. Effects were driven by non-beginner skiers; on average, beginner skiers and all snowboarders were slower than non-beginner skiers and did not adjust their speed in response to the signage conditions.

CONCLUSIONS

Reductions in speed for the slow-sign and slow+patroller conditions compared to the no-sign condition were small (0.5 and 1.1m/s) compared to the variation in chosen skier speed reported in other studies. The small differences in chosen speeds make it unlikely that slow sign and patroller presence alone would produce meaningful reductions in collision likelihood or severity of impacts.