Evaluation of alternative intersection treatments at rural crossroads using simulation software.

OBJECTIVE: Rural roads are characterized by hazardous roadsides and suboptimal geometry yet allow for high travel speeds and unfavorable impact angles. In Victoria, 25% of persons seriously injured and 52% of fatalities occur on rural roads, with 30% occurring at intersections. In the United States, almost twice the number of traffic fatalities occur in rural areas than in urban areas, while accounting for less than half of all vehicle miles traveled and 21% of the population. The choice of safety countermeasure is therefore paramount. Simulation software provides a cost-effective means of analyzing alternative intersection treatments with a view to identifying their effectiveness in mitigating crashes. The aim of this research was to assess the safety benefits of 4 alternative intersection treatments using in-depth crash data with an advanced crash reconstruction process. METHOD: Using a single serious injury real-world crash from the Monash University Accident Research Centre Enhanced Crash Investigation Study and crash reconstruction software, an exemplar rural crash was reconstructed and validated against real-world data. The crash involved a passenger vehicle (European New Car Assessment Programme 5-star) approaching from a minor road and failing to yield at a give-way sign; the posted speed limit was 80 km/h. The vehicle was struck on the right/driver side by a rigid truck (B-vehicle; 1990) traveling on the major approach (100 km/h). The driver of the case vehicle was seriously injured. Four alternative intersection treatments appropriate for the crash site were constructed in computer-aided design software (Rhinoceros Ver. 5): roundabout; rumble strips; a reduced speed limit; and the combination of lower speed limit and rumbles to determine the reduction in crash forces in the presence of the countermeasures. RESULTS: The hypothetical scenarios demonstrate substantial reductions in impact force and different points of impact, resulting in a significantly lower injury severity for the struck driver. Speed limit reduction to 80 km/h on the main approach (from 100 km/h) in combination with rumble strips on both intersection approaches had the most favorable outcome with the crash avoided entirely, assuming speed compliance. DISCUSSION: The findings have implications for understanding the role of speed in crashes and hence the design of effective countermeasures. Simulation software, validated using real-world data, provides a cost-effective means of evaluating alternative intersection treatments for rural intersections. Scaled up, implementing these treatments would have significant safety benefits and reduce the road trauma currently associated with rural roads.

A driving simulator evaluation of potential speed reductions using two innovative designs for signalised urban intersections.

Intersections are typically associated with a higher level of crash risk than other types of facilities on the road network. Standard cross-road intersections are particularly hazardous because by their very design, drivers may travel through at speeds that are incompatible with human biomechanical tolerance should a crash occur. Further, drivers are exposed to dangerous conflict angles, which are likely to result in serious injury. This paper examines the effectiveness of two new intersection designs aimed at restricting potentially dangerous conflict angles while reducing driver speeds through the intersection. These designs, named the "Cut-Through" and the "Squircle", incorporate key features of both signalised intersections and roundabouts. The intersections are controlled by signals similar to a signalised roundabout. Instead of a standard central island, right turning traffic (equivalent to left turns in jurisdictions that drive on the right) cut through the central island, thereby avoiding traffic interlocks and delays that can occur with the traditional signalised roundabout. Across two driving simulator studies, vehicle speed data were collected on approach to and through each of the proposed intersection designs. Performance was benchmarked against equivalent standard signalised cross-road intersections and standard non-signalised roundabouts. Notably, drivers reduced their speeds by approximately 30-40% when negotiating both the Cut-Through and the Squircle compared to the standard signalised intersections. The safety potentials of the two new intersection designs are discussed within the guidelines of the Safe Systems principles.

An exploration of alternative intersection designs in the context of Safe System.

Fatal and serious injury crashes persist at intersections despite current efforts to address this. Little research specifically investigates the role played by existing intersection design in perpetuating serious intersection crash outcomes despite an increasing move to incorporate Safe System design on to roads. This paper identifies design principles deemed important to align intersection design with Safe System approaches, including exploring the impact of speed and angle on overall kinetic energy of a crash. Existing as well as new intersection designs are presented that are believed to incorporate the identified principles. An assessment is made of the alignment of the new and existing designs with the identified principles.

Raised crosswalks on entrance to the roundabout-a case study on effectiveness of treatment on pedestrian safety and convenience.

OBJECTIVE: A common concern in the use of a roundabout is providing adequately for the pedestrian. This unique roundabout layout, which introduces raised crosswalks directly at the roundabout entrance, as opposed to at a car length back, aims at improving safety and convenience for pedestrians at roundabouts. METHODS: A preliminary evaluation of the layout was undertaken to establish its effectiveness in meeting study objectives. A quasi-experimental before-and-after study design was used to compare speeds on approach and immediately prior to the crossing to ascertain potential impact speed and implications for pedestrian safety. Compliance to crossing and crossing time were also compared in relation to safety and convenience outcomes. A questionnaire assessed pedestrian perception of the safety and convenience at the roundabout before and after treatment. RESULTS: Results from this case study indicate that mean approach speeds (free speeds 30 m from crossing) reduced from 32.7 to 30.7 km/h and immediately prior to crossing, mean speeds reduced from 19.1 to 16.3 km/h. There was also a marked reduction in proportions of vehicles traveling at speeds that could elevate risk to pedestrians. Total crossing time after treatment reduced by around 4 s, and crossing compliance increased from approximately half to approximately 90 percent. Survey of pedestrians indicated positive response to the perceived safety and convenience posttreatment. CONCLUSIONS: Preliminary results of the case study suggest positive safety and convenience outcomes. Implications for pedestrian safety include less exposure to traffic and lower risk of serious injury, particularly for elderly pedestrians; convenience outcomes include shorter waiting times to cross and greater compliance to the crossing. A larger study is required to substantiate the findings.

Detection of emergency vehicles: driver responses to advance warning in a driving simulator.

OBJECTIVE: This research evaluated the effects of an advance warning device (AWD) on the safety of driver interactions with emergency vehicles (EVs). The AWD was intended to provide drivers with advance warning of an approaching on-call EV via visual and auditory warnings when the EV was within a 300- to 400-m radius. BACKGROUND: Research suggests that drivers can experience difficulty accurately detecting the distance and direction of approaching on-call EV. In-vehicle technology has not previously been explored as a means of overcoming the limitations of existing EV lights and sirens and improving driver detection of EV. METHOD: An experimental study using an advanced driving simulator examined the effects of the AWD on driving performance in a range of circumstances in which real-world EV crashes and near-misses commonly occur. Each event contained a combination of scenario type (adjacent lane, turning across, car following) and warning condition (control, standard, advance). RESULTS: Data from 22 participants were collected, including measures of speed, braking, and visual scanning. For adjacent-lane and turning-across events, the AWD was associated primarily with reductions in mean speed. The AWD resulted in an earlier lane change to clear a path for the EV in the car-following event. CONCLUSION: The reduction in speed observed was a positive finding, given the relationship between impact speed and injury severity. Response priming emerged as the mechanism underpinning these effects. APPLICATION: Response priming may result in safety benefits in other settings when an advisory warning is presented before the threat can be perceived.

Traffic signal phasing at intersections to improve safety for alcohol-affected pedestrians.

Alcohol-affected pedestrians are among the highest-risk groups involved in pedestrian casualty crashes. This paper investigates the opportunities to use a modified form of traffic signal operation during high-risk periods and at high-risk locations to reduce alcohol-affected pedestrian crashes and the severity of injuries that might otherwise occur. The 'Dwell-on-Red' treatment involves displaying a red traffic signal to all vehicle directions during periods when no vehicular traffic is detected, so that drivers approach high-risk intersections at a lower speed than if a green signal were displayed. Vehicle speed data were collected before and after treatment activation at both a control and treatment site. Speed data were collected both 30 m prior to and at the intersection stop line. The treatment was associated with a reduction in mean vehicle speeds of 3.9 kph (9%) and 11.0 kph (28%) at 30 m and stop line collection points, respectively, and substantial reductions in the proportion of vehicles travelling at threatening speeds with regard to the severity of pedestrian injury. Other important road safety concerns may also benefit from this form of traffic signal modification, and it is recommended that other areas of application be explored, including the other severe trauma categories typically concentrated around signalised intersections.

Perceptual countermeasures to speeding.

An on-road evaluation of two perceptual countermeasure treatments (an enhanced curve post treatment and peripheral transverse edgelines on the approach to an intersection) was conducted over one year to indicate potential for reducing travel speed. Measures included speed and deceleration profiles, braking, and lateral placement observations taken from video recordings at each site. Data were collected before treatment, immediately after treatment, and 12 months after treatment. The results obtained were quite variable across sites and treatments. At curves, speed effects were mixed with both speed reductions and increases observed immediately after and 12-months later. Braking results tended to support travel speed findings and some improvement in lateral placement were also observed at these locations. At intersections, the results were more stable where speed reductions were more common both immediately after treatment as well as longer-term. There were no differences in braking and lateral placement at these straight-road locations. The findings seem to have been unduly influenced to some degree by misadventure and wear and tear at these sites. It is argued that while the effectiveness of these treatments may be site specific to some degree, they do offer a low-cost solution to reducing travel speed at hazardous locations.