Storm, Richard

The objective of this study was to evaluate the safety impacts of increasing the speed limit from 55 mph to 60 mph on two-lane, two-way state highway road segments in Minnesota. An empirical Bayes (EB) before-after analysis was used to estimate crash modification factors (CMFs) for both segments and intersections. The segment analysis showed an 8 percent reduction in total crashes that was statistically significant, alongside a significant 15 percent increase in combined fatal, serious injury, and minor injury (KAB) injury crashes. The range of most of the segment CMFs hovered close to 1. The intersection analysis was split into two groups (all traffic control types and thru-stop control only). The aggregate CMFs for all intersections within these two groups showed, on average, between a 10% and 20% statistically significant reduction in total and injury crashes. Analysis was also performed on four subgroups (3- and 4-leg, lighting/no lighting) within the two main intersection groups. Disaggregating the intersections into further groups led to smaller sample sizes that led to higher standard errors showing a widespread range of CMFs around 1 for the individual crash types and severities. The aggregate estimated crash safety effects (for total and injury crashes) for combined segments and intersection sites showed a reduction in total crashes but an increase in the KAB injury crashes.

This evaluation determined the change in crash frequency, type or severity associated with longitudinal sinusoidal rumble strips on rural two-lane undivided Minnesota roadways constructed between 2018 and 2022. Crash modification factors (CMFs) were estimated using cross-sectional analysis to compare crash experience of locations with sinusoidal rumble strips (i.e., centerline only, centerline and shoulder, or shoulder only) compared to roads with rectangular rumble strips. The cross-sectional analysis matched sites with sinusoidal and rectangular rumble strips using matched-pair comparisons. Negative binomial (NB) or Poisson log-linear regression models were used to model the crashes at all treatment and non-treatment sites. There was a total of approximately 327 miles of treated (i.e., centerline only, centerline and shoulder, or shoulder only sinusoidal rumble strips) and approximately 302 miles of untreated (i.e., centerline only, centerline and shoulder, or shoulder only rectangular rumble strips) on rural two-lane divided roads. Overall, the results of the models indicated no significant differences in crash rates between rural two-lane undivided roads with sinusoidal rumble strips, and rural two-lane undivided roads with rectangular rumble strips.

MnDOT is attempting to address an information gap by conducting a comprehensive and systematic analysis of economic effects of a highway improvement project—the conversion of US 12 to Interstate 394 (I-394). This I-394 Business Impact Study is a first step in documenting credible, local information about the potential business related impacts associated with highway improvements. This research is intended to provide a comprehensive long-term evaluation of the transportation, business, and land development impacts of a major transportation project in the Minneapolis-St. Paul metropolitan area.

The objective of this study was to evaluate the change in crash frequency or severity of varying lateral offset distances of high-tension cable median barriers in Minnesota. Crash and traffic data from 2016 to present were conjoined with roadway cross-sectional data and high-tension cable barrier locations to perform cross-sectional analyses for interstate segments equal to or greater than 0.05-miles long. Negative binomial regression models were estimated and used to develop crash modification factors (CMFs) for the following crash types: total crashes, target crashes, and barrier crashes. In addition to evaluating the impact of lateral offset, a naïve before-after evaluation was completed to quantify the impact of installing high-tension cable barrier.

This evaluation determined the change in crash frequency; type or severity associated with longitudinal rectangular rumble strips on rural two-lane undivided and rural four-lane divided Minnesota roadways constructed between 2012 and 2018. Crash Modification Factors (CMFs) were estimated using cross-sectional analysis to compare crash experience of locations with (i.e.; centerline only; centerline + shoulder; or shoulder only) and without rectangular rumble strips. The cross-sectional analysis matched sites with and without rumble strips using matched-pair comparisons. Negative Binomial (NB) or Poisson log-linear regression models were used to model the crashes at all treatment and non-treatment sites. There was a total of approximately 1;200 miles of treated (i.e.; centerline only; centerline + shoulder; or shoulder only) and untreated sites on rural two-lane roads and approximately 35 miles of treated (i.e.; shoulder rumble strips) and untreated sites on rural four-lane divided roads. On rural two-lane undivided roads; the CMF for centerline + shoulder rumble strips was 0.73 for all crashes; shoulder only rumble strips had a CMF of 0.68 for all crashes. For single vehicle run-off-the-road crashes on rural two-lane highways; the CMF for rumble strips on the centerline + shoulder was 0.68; the CMF for shoulder only rumble strips was 0.76. The CMF for head-on; or opposite direction sideswipe crashes on rural two-lane roads with centerline and shoulder rumble strips was 0.64. On rural four-lane divided roads; the CMF for shoulder rumble strips for all crashes was 0.66 and 0.40 for single vehicle run-off-the-road crashes.

The objective of this study was to evaluate the safety impacts of increasing the speed limit from 55 mph to 60 mph on two-lane; two-way state highway road segments in Minnesota. An empirical Bayes (EB) before-after analysis was used to estimate crash modification factors(CMFs) for both segments and intersections. The segment analysis showed a 7 percent increase in total crashes that was statistically significant; alongside insignificant increases/decreases in injury and run-off-road and head-on crashes. The range of most of the segment CMFshovered close to 1 (essentially meaning that the crashes either remained unchanged or the change was minor). The intersection analysis was split into two groups (all traffic control types and thru-stop control only). The aggregate CMFs for all intersections within these two groups showed that most of the CMFs hovered close to 1. Analysis was also performed on four subgroups (3- and 4-leg; lighting/no lighting) within the two main intersection groups. Disaggregating the intersections into further groups led to smaller sample sizes that led to higher standard errors; showing a widespread range of CMFs around 1 for the individual crash types and severities. The aggregate analysis conducted using all the segment and intersection data showed a minor increase/decrease in the total and injury crashes. This aggregate result along with before-and-after operating speed data from another Minnesota Department of Transportation (2019) study showing that the 85th percentile operating speed remained the same and that mean operating speeds increased by 1 mph following the speed limit increase can lead to aconclusion that the speed limit increase from 55 mph to 60 mph had a very minor to no effect on total and injury crashes or operating speeds.

Report #9 in the Series: Toward a Multi-State Consensus on Rural Intersection Decision Support. This research is part of a larger study to improve rural intersection safety. The Intersection Decision Support (IDS) research project is sponsored by a consortium of states (Minnesota, California, and Virginia) and the Federal Highway Administration (FHWA), whose objective is to improve intersection safety. The Minnesota team's focus is to develop a better understanding of the causes of crashes at rural unsignalized intersections and then develop a technology solution to address the cause(s). In the original study, a review of Minnesota's rural crash records and of past research identified poor driver gap selection as a major contributing cause of rural intersection crashes. Consequently, the design of the rural IDS technology has focused on enhancing the driver's ability to successfully negotiate rural intersections by communicating information about the available gaps in the traffic stream to the driver. In order to develop an IDS technology that has the potential to be nationally deployed, the regional differences at rural intersections must first be understood. Only then can a universal solution be designed and evaluated. To achieve this goal of national consensus and deployment, the University of Minnesota and the Minnesota Department of Transportation initiated a State Pooled Fund study, in which nine states cooperated in intersectioncrash research. This report provides an overview of the crash analysis phase of the pooled fund study for all participating states. This includes patterns identified in severity, driver, and type of error as well as countermeasures previously tried by states.

Report #8 in the Series: Toward a Multi-State Consensus on Rural Intersection Decision Support. This research is part of a larger State Pooled Fund study to improve intersection safety. This report documents the initial phase of selecting a rural, four-lane expressway intersection to deploy a mobile vehicle surveillance system in California. The research team initially looked at four intersections of which none were suitable, thus the California Department of Transportation with the help of the districts chose US 395 and Gill Station Coso Road.

Report #7 in the Series: Toward a Multi-State Consensus on Rural Intersection Decision Support. This is the seventh report in a series that will be used to understand the regional differences in rural intersection crashes. It documents the initial crash-analysis phase of a nine-state pooled fund study for Nevada and concludes that the best overall candidate for test deployment of the IDS vehicle surveillance system is US 50 and Sheckler Cutoff.

Report #6 in the series: Toward a Multi-State Consensus on Rural Intersection Decision Support. This is the sixth in a series of reports sponsored by a consortium of nine states and the Federal Highway Administration to improve intersection safety. To develop an Intersection Decision Support (IDS) technology that potentially can be deployed nationally, regional differences at rural intersections must be understood. To achieve this goal, the University of Minnesota and Mn/DOT conducted a State Poled Fund Study. This report documents the crash analysis phase of the Pooled Fund Study for the State of New Hampshire and concludes that the intersection that is the best overall candidate for test deployment of the IDS Vehicle System is NH 101 and HN 123.