<p>The Road Administration wants to improve safety at a hazardous, rural road intersection near Åkersberga, Stockholm by changing the design of the intersection. The intersection today is a three-way connection with a small road connecting to a four-lane main road, much similar to a motorway with high speeds although with a speed limit of 90km/h. Drivers’ attention and velocity in different designs of the intersection are analysed in this thesis with data from two experiments, ordered by the Road Administration and conducted by the Swedish National Road and Research Institute (VTI). Four alternative designs of the intersection were tested using the VTI-simulator; a narrowing from two to one lane through the intersection, rumble strips, a wooden fence and trees at the road side, and a portal framing the intersection. In addition, the original intersection design, both with and without speed limit signs of 70km/h, were tested for comparisons. In the first of the two experiments, the four alternative intersection designs all had speed limit signs of 70km/h, and in the second experiment the alternative intersection designs were tested without the influence of the speed limit signs of 70km/h. Data used in the analyses are velocity data, lateral position, eye movements, brake data and subjective estimations.</p><p>Subjects were found to look at the critical areas of the intersection in time, independent of intersection design. Only small differences between the intersection designs were found, probably due to width of the main road being a larger design-influence than the measures tested. The results are in favour of the narrowing from two to one lane through the intersection, but traffic density and rhythm make a narrowing difficult to realise at the real intersection. Instead, rumble strips in addition to a speed limit of 70km/h can be recommended, although rumble strips are most likely to increase inattentive drivers’ readiness.</p>

The Road Administration wants to improve safety at a hazardous, rural road intersection near Åkersberga, Stockholm by changing the design of the intersection. The intersection today is a three-way connection with a small road connecting to a four-lane main road, much similar to a motorway with high speeds although with a speed limit of 90km/h. Drivers’ attention and velocity in different designs of the intersection are analysed in this thesis with data from two experiments, ordered by the Road Administration and conducted by the Swedish National Road and Research Institute (VTI). Four alternative designs of the intersection were tested using the VTI-simulator; a narrowing from two to one lane through the intersection, rumble strips, a wooden fence and trees at the road side, and a portal framing the intersection. In addition, the original intersection design, both with and without speed limit signs of 70km/h, were tested for comparisons. In the first of the two experiments, the four alternative intersection designs all had speed limit signs of 70km/h, and in the second experiment the alternative intersection designs were tested without the influence of the speed limit signs of 70km/h. Data used in the analyses are velocity data, lateral position, eye movements, brake data and subjective estimations. Subjects were found to look at the critical areas of the intersection in time, independent of intersection design. Only small differences between the intersection designs were found, probably due to width of the main road being a larger design-influence than the measures tested. The results are in favour of the narrowing from two to one lane through the intersection, but traffic density and rhythm make a narrowing difficult to realise at the real intersection. Instead, rumble strips in addition to a speed limit of 70km/h can be recommended, although rumble strips are most likely to increase inattentive drivers’ readiness.

Fatigue and drowsy driving in the state of Utah has been a causal factor in thousands of crashes over the years and poses a serious threat to public safety. Consequently, the purpose of this research was to evaluate the impact of drowsy driving in the state, to identify locations where fatigue and drowsy driving may be contributing factors to current crashes, and to identify methods to help mitigate these crashes. A 3-year drowsy driving crash rate spanning the years 2002 – 2004 was used to determine which segments of Utah highway are most prone to drowsy driving crashes. Drowsy driving corridors were located on Interstates 15, 70, 80, and 84 as well as United States Routes 89 and 91. Furthermore, State Route 36 also had two drowsy driving corridors. In order to recommend appropriate drowsy driving countermeasures for the drowsy driving corridors, a review of the existing countermeasures was conducted. The existing countermeasures included cable median barrier, rumble strips, rest areas, and drowsy driving freeway signage. The freeway signage is used to alert drivers of the adverse effects of drowsy driving and was the basis for a before-after study as well as a public survey of drowsy driving along Interstate 80 west of Salt Lake City. The before-after study of the drowsy driving freeway signage concluded that the freeway signage has played a part in reducing the number of crashes by as much as 63 percent in the eastbound direction and by as much as 22 percent in the westbound direction. As indicated, a public survey was conducted at two rest areas to supplement the findings of the before-after analysis. Using the 405 completed surveys, 14 Chi-Square tests were conducted with five of the test yielding statistically significant results. Finally, recommendations were made for the 41 drowsy driving corridors resulting from the 3-year crash rate analysis. Drowsy driving countermeasures recommended include: additional shoulder and centerline rumble strips, cable median barrier, guardrail replacement, and drowsy driving highway signage. Drowsy driving countermeasures not yet implemented but which should be considered by the Utah Department of Transportation are transverse rumble strips, wider longitudinal pavement markings, in-lane pavement markings indicating “AVOID FATIGUE DRIVING,” minimizing edge drop off, flattening slopes in clear zones, and adding a modified rest area.