The impact of rural expressway environments: drivers' attention allocation to variable message signs.

Variable Message Signs (VMS) are implemented at varying locations of the expressway. In this study, we compared the drivers' attention allocation to a 'drive safely' message on several VMS gantries that were located at six sections of typical expressway conditions in Qatar. We investigated how the expressway drivers perceive the VMS when implemented in different driving conditions (e.g. higher truck or car density) and surrounding environments (landmarks, buildings, bridges, exits, etc.). Besides, it was studied whether the driver's attention to the speedometer and the side mirrors was influenced. The eye-tracking data of seventy-nine drivers from the State of Qatar was analyzed, while driving in a driving simulator. It was found that a higher truck density on the expressway before the VMS location would lead to a delayed time-to-first-fixation and a lower fixation count to the VMS. The results of an ANOVA revealed that the expressway environment did not influence the drivers' average fixation duration to the speedometer and side mirrors when encountering the VMS. Therefore, no interfering effects must be expected for 'drive safely' messages at VMS locations with varying expressway traffic and surrounding conditions.

The evaluation of decorated camera housings - A driving simulator study.

Traffic enforcement cameras can lead to unwanted side-effects. For instance, red-light cameras at intersections can increase the chance at rear-end collisions, probably caused by slowing down abruptly. Additionally, on the highways, speed cameras could lead to kangaroo-jumps in driving speed. Warning drivers about cameras is a possible solution. Cameras that are uncommonly decorated (e.g. colored in pink or in yellow) may provide better conspicuity compared to those in standard colors like gray. However, besides warning drivers about their presence, more conspicuity of cameras could also distract drivers from the primary driving task. Therefore, the impact of such decoration on safety is unclear. This study evaluates different decorated designs of the camera housing and how such decoration may influence camera's conspicuity and induce distraction while driving. Three camera colored-designs were evaluated (gray, pink, and a mixture of yellow and black) using a driving simulator. Fifty-four participants drove nine different conditions, i.e. three camera-designs in three roadway-settings (basic highway segments, intersections operating during the amber-phase, and intersections with a bicycle-lane). Subjective and objective measures allowed to assess if: 1) decorated camera housings increased conspicuity, 2) signs of distraction could be found, and 3) driving was influenced. In addition to the detection success rate, other eye-tracking parameters were: time-to-first-fixation, fixation count, and average and total fixation duration. Driving measures, i.e. speed, acceleration or deceleration rate, lane-keeping behavior, and minimum time-to-collision, were included to assess if the tested camera-designs impacted driving behavior. Moreover, a post-drive questionnaire assessed the participants' opinions. Using camera colored-designs improved the camera's conspicuity. However, driving measures remained comparable across the three camera-designs. Although the subjective data indicated some distraction from the decorated cameras, clear indications for an effect on traffic safety were lacking. Meanwhile, a little over half of the respondents supported camera decoration. The current study does not allow firm conclusions, and additional research is recommended.

Investigating the effect of marking and delineation treatments on driver behavior at highway exit gore areas.

Highway exit gore areas are common and essential components of highway networks everywhere. Drivers need to navigate, decelerate, and change lanes at exit gore areas through specified and compacted geometry. This makes exit gore areas potentially crash-prone locations. Studies analyzed factors contributing to crashes at exit gore areas. Although marking and delineation techniques can play a major role in enhancing safety, traffic control devices that serve this end were not given sufficient attention in recent research. Furthermore, the currently used marking and delineation treatments are widely different around the world and deploy devices of various forms, shapes, sizes, and colors. The Flemish Agency for Roads & Traffic (AWV) launched a study to explore the feasibility of adding colored and sizeable eye-catching objects, mounted or grounded exactly at the physical nose, to attract driver's attention and improve driving performance. The eye-tracking and driving behavior of 49 Belgian drivers was investigated in a driving simulator. Participants were also queried about the conspicuity of the control devices and their personal preferences. The results were univocal for situations including a guardrail. Using two mounted panels together, i.e., the horizontal and the vertical, scored better on all levels than the horizontal panel alone. The bigger surface size of the traffic control device significantly improved driving performance and was also favored by the participants. Situations without a guardrail lacked such clear results, which were mixed depending on the measure at hand. A larger size of a grounded object-marker, again, improved driver's performance. Findings concerning the colors red or green appeared to favor red, although this was less univocal. These findings are aimed to spark ideas for further research and to assist practitioners and policy-makers in better designing exit gore areas while achieving more consistency and safety.

Optical pavement treatments and their impact on speed and lateral position at transition zones: A driving simulator study.

Transition zones are a road section where posted speed drops from higher to lower limits. Due to the sudden changes in posted speed limits and road environment, drivers usually do not adapt to the posted speed limits and underestimate their traveling speed. Previous studies have highlighted that crash rates are usually higher in these sections. This study aims at improving the safety at transition zones by introducing perceptual measures that are tested using a driving simulator. The proposed measures are speed limit pavement markings with a gradual increase of brightness and/or size that were placed at transition zones in simulation scenarios replicating the real-world environment of the Doha Expressway in Qatar. These innovative measures aim to produce the impression of increased speed that could stimulate drivers to better adapt speed limits. The driving behavior of 81 drivers possessing a valid Qatari driving license was recorded with a driving simulator interfaced with STISIM Drive® 3. Results showed that pavement markings combining size and brightness manipulations were the most effective treatment, keeping drivers' traveling speed significantly below the traveling speed recorded in the untreated control condition. In this regard, the maximum mean speed reductions of 5.3 km/h and 4.6 km/h were observed for this treatment at the first transition (120 to 100 km/h) and second transition (100 to 80 km/h) zones, respectively. Regarding the variations in drivers' lateral position, the results showed that the proposed pavement markings did not negatively influence drivers' lateral control on the road as the maximum observed standard deviation of lateral position was around 0.065 m. This study shows that the proposed pavement markings are recommended for improving the speed adaptation of drivers in the transition zones.

Drivers' estimation of their travelling speed: a study on an expressway and a local road.

Correctly estimating the travelling speed is essential for safety on the roads to ensure safer interactions with other drivers and to avoid violations of traffic regulations. Therefore, it is important to create understanding of the pattern of speed perception of drivers and the influencing factors. This study invited 40 drivers to participate in a field experiment measuring speed perception. The experiment was conducted using a test car equipped with high fidelity Global Positioning System (GPS). Data were collected for two settings (hidden versus revealed speedometer) and four requested speeds (50, 70, 80 and 100 km/h). An analysis of variance test was conducted along with separate t-tests and cumulative distributions for each speed independently. The results clearly show that there were significant differences in perceived speed between a hidden and revealed speedometer, between the first and second trial and among all the requested speeds. Participants drove significantly faster for all the requested speeds in the hidden speedometer setting. This shows that participants underestimated their speed. In case of complex situations, drivers may not be able to rely on speedometers and may cause a violation of law, unintentionally. Therefore, it is recommended to jurisdictions to consider these results while making decisions regarding speed management.