Abstract. Transportation sustainability is adversely affected by recurring traffic congestions, especially at urban intersections. Frequent vehicle deceleration and acceleration caused by stop-and-go behaviours at intersections due to congestion adversely impacts energy consumption and ambient air quality. Availability of the maturing vehicle technologies such as autonomous vehicles and Vehicle-To-Vehicle (V2V) / Vehicle-To-Infrastructure (V2I) communications provides technical feasibility to develop solutions that can reduce vehicle stops at intersections, hence enhance the sustainability of intersections. This paper presents a next-generation intersection control system for autonomous vehicles, which is named ACUTA. ACUTA employs an enhanced reservation-based control algorithm that controls autonomous vehicles' passing sequence at an intersection. Particularly, the intersection is divided into n-by-n tiles. An intersection controller reserves certain time-space for each vehicle, and assures no conflict exists between reservations. The algorithm was modelled in microscopic traffic simulation platform VISSIM. ACUTA algorithm modelling as well as enhancement strategies to minimize vehicle intersection stops and eventually emission and energy consumption were discussed in the paper. Sustainability benefits offered by this next-generation intersection were evaluated and compared with traditional intersection control strategies. The evaluation reveals that multi-tile ACUTA reduces carbon monoxide (CO) and Particulate Matter (PM) 2.5 emissions by about 5% under low to moderate volume conditions and by about 3% under high volume condition. Meanwhile, energy consumption is reduced by about 4% under low to moderate volume conditions and by about 12% under high volume condition. Compared with four-way stop control, single-tile ACUTA reduces CO and PM 2.5 emissions as well as energy consumption by about 15% under any prevailing volume conditions. These findings validated the sustainability benefits of employing next-generation vehicle technologies in intersection traffic control. In addition, extending the ACUTA to corridor level was explored in the paper.

The absence of roadway lighting during the night results in a disproportionally large number of traffic crashes and fatalities. Past research on safety effects of roadway lighting involved mostly qualitative studies and focused on intersections and rural roads rather than freeways and interchanges. However, it is desirable to quantify the safety benefits of lighting for cost–benefit analysis and eventual decision making on lighting installations. This paper aims to develop nighttime crash prediction models for roadway lighting in the form of safety performance functions (SPFs). A pilot study on all freeways and expressways in the jurisdiction of Dane County, Wisconsin, was conducted. The crash data collection covered five years' nighttime crashes on all freeways, expressways, and interchanges in Dane County. Nighttime crashes were identified and light-pole data were collected along with traffic and geometry data. On the basis of the data, six SPFs were developed for freeway segments and interchange ramps under lighted and unlighted conditions. Results showed that the number of lanes was a significant factor for interchange ramps. Entry ramps had significantly higher numbers of crashes than did exit ramps under unlighted conditions. Similar results were observed for interchange freeway segments and noninterchange freeway segments. The international roughness index, used as a surrogate for pavement friction values, was significant for all freeway segments' SPFs. Severity distribution functions were also developed. Results showed that the largest safety benefit could be achieved by installing lighting at interchange segments, entry ramps, or exit ramps with annual average daily traffic greater than 10,000 vehicles per day.

On-duty struck-by crashes are defined as traffic crashes that involve police officers, roadway workers, firefighters, and emergency medical technicians–first responders who are hit by a motorist while on duty assisting at an incident or in a work zone. The objective of this research was to summarize and analyze struck-by crashes on the basis of Wisconsin crash data. Crash data from 2000 to 2010 on Wisconsin's state trunk network were selected from the WisTransPortal database. Data reduction included several filtering steps and manual identification; 265 crashes were identified as struck-by crashes, and their characteristics and contributing factors were analyzed. Responder and worker struck-by crashes were analyzed separately because of their different characteristics, and all state trunk network crashes from 2000 to 2010 were used as a comparison group. Results showed that for responder crashes, police officers were the predominant victim. A large proportion of responder crashes occurred on rural Interstate highways. Speeding or driving too fast for conditions was the key driver factor that led to struck-by crashes, and adverse roadway and weather conditions were the most significant environmental factor. Most emergency responder struck-by crashes occurred when responders were assisting at traffic crashes. However, flaggers hit by surrounding traffic accounted for approximately half of all worker struck-by crashes. Worker crashes were uncorrelated with adverse weather, roadway, or lighting conditions. Inattentive driving was the most significant contributing factor. These results provide the basis for countermeasures to reduce struck-by crashes involving emergency responders and roadway workers.