Effective access management is critical to the safe and efficient operation of roadway corridors. Access management is particularly important near signalized intersections, where adjacent driveways exacerbate the crash risks created by conflict points at the primary intersection. This study examines the relationship between crash risk and access spacing in the vicinity of 415 signalized urban intersections. The frequency of access points near each signalized intersection of interest was collected to examine the differences in experienced crash frequency over a five-year period. Additional information about each access point was collected, including details of turning movement restrictions and estimated driveway volumes. A series of buffers of varying radii were considered to examine how crash rates varied based upon the spatial proximity of access points to each signalized intersection. In addition, traffic volume and roadway geometric information was collected and utilized as a part of this evaluation. A series of crash prediction models were estimated to discern how crash rates varied based upon the access point density on the intersection approaches along the major (i.e., higher volume) roadway. As the number of access points increased, the crash rates also increased. This relationship was consistent in direction, but varied in magnitude, depending on the size of the buffers, which varied in radius from 50 ft to 600 ft at 50-ft intervals. The number of crashes by location was also shown to vary based upon the number of travel lanes, the number of intersection legs, and the land use type of the adjacent driveways.

Move-over laws are intended to enhance the safety of road agency and law enforcement personnel who are working on or near the roadway. This study examined driver behavior through a series of field studies where these types of vehicles were located on the outside shoulder of a freeway with their lights activated. The study also evaluated the use of upstream dynamic message signs (DMS) to discern whether targeted safety messages had any impact on behavior under this scenario. Upstream and downstream speed and lane position data were collected from vehicles originally traveling in the rightmost lane upstream of the DMS and emergency/service vehicle at two locations in Michigan. Logistic regression models were estimated to assess driver compliance with the law while considering important contextual factors, such as the type of vehicle on the shoulder and the message displayed on the DMS. The results indicated that drivers were more likely to move over or reduce their speeds when a police car was located on the shoulder as compared to a transportation agency pickup truck. In general, the type of message displayed had minimal impact on driver behavior. The one exception showed that drivers were likely to drive at or below the speed limit when targeted move-over messages were shown as compared to standard travel time messages. For all message types, both speed and lane compliance improved if the roadside vehicle was a police car.

Cellular telephone use has increased significantly in the United States as 97% of residents now own some type of cell phone. The ubiquity of cell phones has introduced concerns with respect to traffic safety as cell phone-related distractions have been shown to affect driving ability and increase crash risk. Various countermeasures have been implemented to address this issue, including public outreach campaigns and targeted enforcement activities. However, the efficacy of such strategies has been the subject of limited research. This paper examines cell phone use rates in consideration of enforcement activities in conjunction with targeted safety messages on roadside dynamic message signs. Two phases of enforcement were conducted in two urbanized areas of Michigan. Data were collected before, during, and after the enforcement period. A two-way random effects logistic regression model was estimated, and the results showed that cell phone use rates were lower during and, particularly, after the enforcement activities were conducted. Use rates were also found to vary based on age, gender, and race, allowing for the identification of target groups for public awareness and outreach campaigns. Use rates were also lower at freeway exit ramps as compared to signalized and stop-controlled surface street intersections. Lastly, cell phone-specific safety messages were associated with lower use rates compared with other message types, suggesting a potential synergistic effect.

Posted speed limits inform drivers of the legal maximum allowable speed. In contrast, advisory speeds provide recommendations to drivers based on highway design, operating characteristics, and conditions. Various studies have investigated the safety impacts of speed limit changes, particularly on high-speed rural highways. One area of particular concern on such roadways is the approach to exit ramps that require substantive speed reductions, such as loop ramps. To date, there has been limited research examining the safety impact of the differential between the mainline speed limit and the lower exit ramp advisory speeds. This study aims to evaluate this relationship through the estimate of a series of safety performance functions. Random effects negative binomial regression models were estimated using data from 187 exit ramps where advisory speed signs are present throughout Michigan. The analyses were conducted based on a five-year period from 2014 to 2019, excluding 2017 data because of speed limit increases. In addition to speed differentials, various roadway characteristics such as deceleration lane length and curve radius were also evaluated. Results indicate that crashes increased as the difference between mainline and ramp speed increased. Crashes were also shown to decrease on ramps where the upstream deceleration lane length was greater than the minimum recommendation as per current design guidance.

Research was conducted to assess the effectiveness of a dynamic speed feedback sign (DSFS) as a speed reduction strategy at speed transition zones along five high-speed rural highways in northern Michigan. The DSFS was positioned on the shoulder in advance of the reduced speed limit at each community and was programmed to display speeds of approaching vehicles alternating with the upcoming reduced speed limit. Using handheld LIDAR guns, vehicle speeds were tracked through each speed transition area before and after installation of the DSFS. The DSFS was found to have a significant speed reduction effect throughout each of the five speed transition zones. The speed reductions generally began when the DSFS came into the motorists’ view, and the speed reduction effect increased as motorists approached DSFS. The greatest speed reduction effects were observed at the DSFS location itself, where speeds were 3.2 to 7.8 mph lower with the DSFS present, and these reductions were sustained on entry to the community. Similarly, drivers were 78.8 to 92.4% less likely to exceed the reduced speed limit with the DSFS present. Positioning the DSFS further upstream typically resulted in earlier speed reductions, although this effect became negligible once vehicles reached the reduced speed zone entering the community. Based on the study findings, continued use of DSFS for speed management at speed transition zones entering communities on high-speed rural roadways is recommended. When used in this context, the DSFS should be positioned 250 to 650 ft upstream of the reduced speed limit.