Knickerbocker, Skylar

This study is a complement to Evaluation of Intersection Collision Warning Systems in Minnesota (2017-38), which was published in October 2017. That project evaluated behaviors such as type of stop for drivers on the minor approach in the presence of intersection collision warning systems (ICWS). This project was a follow-up to that study and compared speeds along the major street approaches at ICWS treatment sites after installation of the system to determine whether the ICWS provided any measurable impact on speed when drivers on the major street were presented with a message from the system (activated) versus when drivers were not presented with a message (not activated). The study found that mean and 85th percentile speeds were lower on the major approach when the ICWS was activated compared to when it was not activated. However, the differences were minor. As a result, the system is expected to reduce speeds, but only a modest impact is expected in terms of mainline drivers.

Winter weather and its corresponding surface conditions impact the safety and mobility of thousands of motorists annually. Highway agencies spend millions of dollars in resources and personnel in an effort to ensure safe and efficient travel. One such strategy is to use dynamic message signs (DMS) that have been deployed across the state to alert drivers of conditions ahead based on data from roadside sensors. This type of advisory system can provide real-time information, allowing drivers to adjust their driving behavior to the conditions ahead. The objective of this project was to analyze traffic behavior along a specially instrumented portion of the US 12 corridor under various winter weather conditions when advisory messages triggered by roadside pavement sensors were provided via DMSs between Delano and Maple Plain, Minnesota. Temporary traffic sensor data upstream and downstream of the DMS are used to evaluate traffic flow metrics during winter weather conditions as compared to baseline conditions. In the eastbound direction, statistically significant reductions in mean and 85th percentile speeds of 3.5 mph and 2.9 mph, respectively, were identified. The westbound direction experienced mixed results, with a mixture of statistically insignificant changes as well as statistically significant increases and decreases in speeds. It is assumed that other factors were influencing driver behavior in this westbound direction. There were indications of positive effects on vehicle gaps when evaluating all events combined that were statistically significant but not when evaluating individual winter weather events.

Reduced traffic volumes resulting from COVID-19, along with the strain on enforcement during the pandemic, are thought to have produced higher speeds and more aggressive driving. Understanding the magnitude of speeding and other driver behaviors requires measurement and contrast. This project quantifies reductions in volume and the resulting differences in travel speeds across Minnesota along regular roads and within two work zones prior to and during the novel COVID-19 pandemic. The work includes a review of total crashes as well as fatal and serious injury crashes and includes a survey of law enforcement opinions. Findings based on 125 Automatic Traffic Recorders (ATR) and traffic Sensors quantify volume reductions, which, of course, were lower in 2020 but which varied considerably by location and month. Average speeds overall along with both the number and percentage of vehicles traveling greater than 15 mph over the posted speed limit increased in 2020. This information supports benchmarking and agency decision making.

The Minnesota Department of Transportation (MnDOT) is investing significant resources in intersection collision warning systems (ICWS) based on early indications of effectiveness. However; the effectiveness is not well documented; and negative changes in driver behavior at treatment intersections may affect drivers overall; resulting in a spillover effect. Moreover; the effectiveness of ICWS may decrease if drivers do not perceive a change in the dynamic messages. Therefore; the objectives of this research were to (1) evaluate driver behavior at mainline and stop-controlled approaches for intersections with and without ICWS and (2) assess the traffic volume range and limits where the system is nearly continuously activated and is likely to lose its effectiveness. Video data were collected at five treatment and corresponding control intersections; and various metrics were used to compare changes in driver behavior. In general; no negative behaviors were noted for either treatment or control intersections.

This research effort provided the Minnesota Department of Transportation (MnDOT) with field data on the performance of pavement marking materials when used as rumble stripes on MnDOT roadways. These field efforts provide a perspective on the impact that both wear and winter maintenance practices have on retroreflectivity. Given that these markings were installed by a variety of MnDOT contractors and at different times and roadways, this report also serves to document the range of retroreflectivity provided to drivers at any given time on similar two-lane MnDOT roadways under the installation practice guidelines at the time of installation (2012 to 2013). More specifically, these measurements consider the difference in retroreflectivity provided by direction of travel (e.g., for the same marking, what is the retroreflectivity while driving northbound versus southbound?) and by roadway. The long-term evaluation collected field measurements both initially and after two winters (18 months) for centerline rumble stripes only and on seven segments over three different roadways. The in-service evaluation included new centerline and profile rumble stripEs, all of which were installed as part of the 2013 mill and overlay projects on bituminous surfaces within District 4 on two-lane MnDOT roadways. The retroreflectivity data were collected one winter (approximately 12 months) after installation with no initial measurement data being available. This effort included measuring the centerline rumble stripe performance over eight segments on four different roadways and the profile rumble stripe performance over 18 segments on 10 different roadways.

The objective of this research was to conduct a field trial to evaluate the marking performance of different combinations of pavement marking materials and installation practices on challenging surfaces. The trial included a range of pavement marking products over varied roadway characteristics to assess the performance of different marking materials over different challenging surfaces by product, thickness, bead package, and whether or not a primer was applied. The research team worked with the technical advisory panel (TAP) to document pavement marking performance on several municipal roadways within the city of Eden Prairie and to organize and prepare for field testing of different marking materials on both a seal coat and micro surface roadway. These projects provide pavement marking performance on challenging surfaces information over different conditions (traffic levels and line types) apart from the MnDOT research test deck scenarios. These results provide MnDOT with a basis to consider pavement marking striping practices on challenging surfaces in terms of performance and cost. The high-build materials (primer plus VISILOK) and epoxies showed similar performance, which provides a good basis for material selection.