All posts by mndotresearch

New Project: Driver Comprehension of Flashing Yellow Arrows

Flashing yellow arrow indicators have been deployed at many signalized intersections in recent years to control left-turn movements and improve traffic flow.

When illuminated, the flashing yellow arrow allows waiting motorists to make a left-hand turn after yielding to oncoming traffic. 

The Federal Highway Administration considers flashing yellow arrows to be a significant safety improvement over traditional yield-on-green indicators, which are believed to be less intuitive. However, motorist complaints and some high-profile crashes indicate that there is still some level of driver confusion.  

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Study: Public Transit Benefits Exceed Costs in Rural and Small Urban Areas

The benefits of Minnesota’s rural and small urban transit systems exceed the costs of services, according to a study sponsored by the Minnesota Department of Transportation (MnDOT). For every dollar spent to provide transit services in Greater Minnesota, benefits worth $2.51 are shared throughout the communities, according to the “Measuring the Economic Benefits of Rural and Small Urban Transit Services in Greater Minnesota” report.

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Guidebook helps cities and counties choose tools for managing fleets

Managing a fleet of trucks, heavy equipment, and other vehicles challenges road agencies large and small. While large agencies like MnDOT use software and specialized administrators to manage fleet management systems electronically, city and county agencies often do not. For some small agencies, fleet management may fall to a shop mechanic or two.

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Leveraging Existing Inductive Loops to Classify Highway Vehicles

Researchers evaluated the use of existing inductive loop installations in Minnesota for vehicle classification. Results showed that inductive loops may be effective at identifying and classifying individual vehicles as they pass, but the system will require further refining for Minnesota use.

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Recycling Asphalt Pavement Offers Strong Alternative to New Aggregate Base

In a newly completed study, researchers found that stabilized full-depth reclamation has produced stronger roads for commercial loads in Minnesota, and the method shows promise for uses in rural agricultural areas. How much greater the strength gained with each stabilizing agent is better understood, though not conclusively.

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Testing Methods for Crack Resistance in Asphalt Materials

The Minnesota Department of Transportation is working with other state agencies in a pooled fund study to improve methods for testing crack resistance of asphalt mixtures. To expand options further, MnDOT asked researchers to evaluate alternative tests with standard lab equipment. The new tests produced repeatable results. Methods include the semicircular bend (SCB) test in a nontypical configuration, a dynamic modulus test of smaller asphalt mixture samples, a bending beam rheometer (BBR) test of mixtures, and a BBR of asphalt material for binder selection.

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Impact of Arterial Bus Rapid Transit on Traffic and Users

Video and statistical analyses showed that arterial bus rapid transit (ABRT) along Snelling Avenue in Minneapolis-St. Paul had no significant impact on traffic volume and wait times at intersections. Survey results demonstrated that users prefer the A Line over local bus service and consider it roughly equivalent to express bus, light rail and commuter rail service. Though ABRT has not converted automobile drivers to transit riders, users enjoy its easy payment format, cleanliness, route service and convenience. This study also provided recommendations for future ABRT line design considerations.

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New Tools to Optimize Truck Station Locations

The Minnesota Department of Transportation (MnDOT) has 137 truck stations across the state. These stations house and allow maintenance of MnDOT highway equipment as well as provide office and work space for highway maintenance staff. Within 20 years, 80 of these stations will need to be replaced as they reach the end of their effective life spans. Researchers developed a geographic information system based modeling tool to determine the most effective locations for truck stations in the state. Using data from many sources, a new research study has determined that MnDOT could rebuild 123 stations, relocate 24 on land available to MnDOT and combine two. MnDOT would save millions of dollars using the location optimization alternatives over the 50-year life cycle of a typical truck station.

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Study Suggests 70 Percent RAP for Minnesota Gravel Road Surfaces

Researchers examined mixtures of recycled asphalt pavement (RAP) and aggregate for new gravel road surface layers in the lab and in the field. Although test results did not align perfectly, and field results were somewhat uneven, findings suggest that mixtures with 70 percent RAP content can reduce dust generation. After a year of service these roadways can match all-aggregate gravel road performance in terms of strength, but with a smoother ride.

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