Search Content

While High Occupancy Vehicle (HOV) lanes have been used for decades as a strategy for mitigating congestion, research has shown that they are not always effective. A 2001 study of the I-394 and I-35W HOV lanes in Minnesota found that the HOV lanes were on average underutilized, moving fewer people than the General-Purpose Lanes (GPL) even with the increased number of passengers per vehicle. To address the issue of underuse, in 2003 the Minnesota Legislature authorized the conversion of the I-394 HOV lanes into High-Occupancy Toll (HOT) lanes, named the MnPASS Express Lanes. The MnPASS lanes operate using a fully dynamic pricing schedule, where pricing is dictated by the level of congestion in the HOT lane. To better understand the nature of HOT lanes and the decisions of their users, this study explored the possibilities for a microscopic traffic simulation-based model of HOT lanes. Based on a series of field studies where the price of the toll was changed while observing changes in demand in the HOT lane, models describing the lane choice behavior of MnPASS users were developed and calibrated. These models interfaced with the traffic simulation software Aimsun through a number of extension modules and tested on the two MnPASS corridors of I-394 and I35W corridors in the west and south suburbs of Minneapolis, Minnesota. The integrated HOT simulation tool was also used to develop and test a number of alternative pricing strategies including a more efficient version of the current strategy.

When looking at measures of fatal and severe-injury crashes; roundabouts have demonstrated improved safety performance compared to traditional signalized intersections. Despite this; when it comes to less severe crashes; multilane roundabouts fail to provide a similar benefit. Previous research into this topic has identified behaviors that are associated with crashes in two-lane roundabouts; with yielding violations and turn violations generally being the largest contributors to crashes. This study sought to build on that work by expanding the data collection effort to include more sites and relate the frequency of individual behaviors to specific design features. Ultimately; four roundabouts were chosen for data collection and analysis; with two of them being full 2x2 roundabouts and the other two half-2x2. These locations were University Dr. S and 5th Ave. S in St. Cloud (half-2x2); 185th St. W and Kenwood Trail in Lakeville (full-2x2); and TH-22 and Adams St. (half-2x2) and TH-22 and Madison Ave. in Mankato (full-2x2). In the last two; changes in traffic control were implemented to reduce failure-to-yield crashes; and the study compared the driver behavior before and after the interventions. In general; the collective results show that the problems observed in the earlier site are present in all of the other sites with scale variations prompted by geometric and traffic control design elements. For example; in the St. Cloud roundabout; an increased rate of right-from-inner-lane turn violations were observed; which can be attributed to the sharper deflection angles present. Additionally; from the aforementioned roundabout as well as the one in Lakeville; it was concluded that turn violation rates are affected on the single or multilane geometry of the links approaching the roundabout. Single-lane roads result in fewer left-from-outer-lane violations. Overhead lane designation signs result in reduced turn violations similar to the earlier studies' interventions in the approach lane markings. Unfortunately; apart from confirming the trend; no successful design or intervention was discovered regarding yield violations.

Connected and Automated Vehicles (CAVs) are expected to affect the foundations of transportation operations and roadway maintenance as they become more prevalent on the roadways. This report is an effort to address this complex subject for the various owners; agencies and stakeholders involved in traffic operations. It discusses the connected vehicle ecosystem and its background; potential CAV applications; types of communication and hardware required for CAV systems; and recommendations to local road owners. The report also includes a survey sent to local road owners to assess the current readiness of the transportation system for CAVs. Although it is too early to give specific recommendations; general guidance is provided for road owners to begin preparing for the future of CAVs.

Detailed Intersection Control Information (ICI); including timing; phasing; geometric; and demand attributes; is an increasingly important resource for researchers; consultants; and private sector companies for many applications; including development of traffic models and technologies such as vehicle information or automation systems. While this information has historically been difficult to distribute due to variations in the availability and format across the numerous jurisdictions that operate signals; recent trends toward increased use of Central Traffic Signal Control Systems (CTSCSs) have made creation of a unified; standardized system for organizing ICI more feasible. To help work toward this; in this project researchers interviewed and surveyed signal operation engineers and transportation modelers throughout Minnesota to learn how different jurisdictions manage information relating to their signals and how this information is used for operations and planning. With this information; researchers developed a comprehensive Unified Set of Intersection Control Information (U-ICI) that contains all the information required to describe the control of an intersection in a format that is readable by both humans and machines. Along with this; researchers evaluated the availability of this information and the feasibility of using existing CTSCS applications to store this information. While the researchers conclude that it is not feasible to use these applications to store all of the U-ICI; the applications will likely make the process of implementing and populating such a system easier. Though some information may be contained in formats that will require manual effort to digitize; the up-front effort to do so will be a worthwhile pursuit.

The Smart Work Zone Speed Notification (SWZSN) system aims to alleviate congestion; queuing; and rear end crashes in work zones by informing drivers of the speed of the downstream segment using a type of portable Intelligent Lane Control System (ILCS); Portable Changeable Message Signs (PCMS). The hypothesis was that drivers; knowing the speed up to 1 mile downstream; will slow down early or at least be alert and perform smoother decelerations. Video of the SWZSN was analyzed over two years of operation by the Minnesota Traffic Observatory. Overall; the system resulted in beneficial reductions of selected decelerations by the drivers. In situations where the messages communicated to the drivers were consistent and accurate; reductions of more than 30% in the selected deceleration rates were observed. Unfortunately; there were several cases where counterproductive or misleading messages were communicated to the drivers; prompting relative increases to the selected deceleration rates. The most important observation; stemming from both positive and negative influences; was that the speed notification system was noticed by drivers and resulted in a statistically significant influence on driving behavior; unlike other driver alert systems.

An interactive presentation describing frequently asked questions about Connected and Autonomous Vehicles (CAV). The presentation is divided into five sections: General, Timing/Preparation, Policy/Standardization, Safety, Rural, and Resources.

The Tipping Point – What COVID-19 Travel Reduction Tells Us About Effective Congestion Relief uses observed data collected before and during the COVID-19 pandemic in the Twin Cities metropolitan area to answer a question with important implications for highway investment planning and travel demand management: At what level of vehicle miles traveled (VMT) does congestion significantly decline or disappear? The study pursues this question through a series of statistical analyses identifying inflection points in the relationship between regional VMT and congestion. The study also looks at the relationship between VMT and congestion at the corridor level to assess the sensitivity of congestion on specific roadways to changes in travel demand. This analysis categorizes Twin Cities freeways based on congestion frequency, highlighting the corridors expected to become congestion free as VMT declines and the corridors expected to remain congested.

Pedestrian-Activated Crossing (PAC) systems have been shown to have a generally positive impact on driver yield rates. However; there has been insufficient research on the effect PAC treatments have on pedestrian crash rates; and there is little guidance as to when and where each treatment should be used. This study estimates the effects of PACs on pedestrian crash rates using Monte Carlo simulation and examines the relationships between driver yield rates and a variety of treatments and site designs by conducting an observational study using video data from 34 locations. The simulation outcomes suggests that while the percentage of yielding drivers might be a useful indicator of pedestrian level of service; it is less helpful as safety surrogate. This could be because a driver's yielding to a pedestrian; as observed in field studies; might not be the same behavior as a driver attempting to stop during a vehicle/pedestrian conflict. The observational study shows that the number of lanes to cross at a crossing is positively correlated with the rate at which pedestrians activate the system; but it is not correlated with the delay. Additionally; the study showed that the effect of PAC systems is most pronounced at sites with a higher number of movements conflicting with the crossing or poor visibility from upstream without signs warning drivers of an upcoming crosswalk.

Appendix E (FULL EXAMPLE OF ICI FROM DIVERGING DIAMOND INTERCHANGE AT HENNEPIN COUNTY ROAD 144 AND TH-101 IN ROGERS, MN) was published separately from report 2019-14, Evaluation of a Central Traffic Signal System and Best Practices for Implementation.

Dynamically priced High Occupancy Toll (HOT) lanes have been recently added to the traffic operations arsenal in an attempt to preserve infrastructure investment in the future by maintaining a control on demand. This study focuses on the operational and design features of HOT lanes. HOT lanes' mobility and safety are contingent on the design of zones ("gates") that drivers use to merge in or out of the facility. Existing methodologies for the design of access zones are limited to engineering judgment or studies that take into consideration undersized amount of observations. This project capitalized on the results of an earlier project that performed an assessment of safety and mobility on the HOT facilities in Minnesota highlighted the issues involved in either designs. The product of this project; the MnPASS Access Design application; provides a tool for traffic managers and planners to examine the conditions within an existing or prospective corridor and the distribution of shockwave lengths which are expected. From the distribution of shockwave lengths; decisions can be made regarding access restriction on the HOT lane to ensure that drivers do not attempt to make lane changes at locations prone to dangerous conditions. This tool provides support for the managers and planners by aggregating the entire behavior of the HOT lane within the corridor into a framework for simplified consideration.