MULTIMODAL — Cities across the country are installing separated bike lanes (SBLs) to encourage bicycling as a means of transportation, but current SBL design guidance is incomplete. Researchers collected all existing SBL guidance to determine the gaps in knowledge. They interviewed planners and designers to learn about their challenges. Then they surveyed hundreds of Minnesota bicyclists about their bike lane preferences, including aspects of winter riding. SBL design guidance is evolving. This project gathered an enormous amount of data, practitioner perspectives and user information to fill in the gaps of SBL design knowledge. It is a step toward making safe urban bike networks more common.

Report 2021-12

ENVIRONMENTAL — MnDOT and local agencies control stormwater runoff from roadways through a range of settlement, filtration and infiltration facilities, such as wet ponds, infiltration basins, trenches and swales. Infiltration facilities have been used for more than 30 years, but a high rate of failure has been tied to inaccurate determination of soil infiltration rates. Researchers developed new tools and protocols to provide designers and engineers with the accurate infiltration measures they need, from initial site selection through construction. These tools and methods will support the development of successful stormwater infiltration facilities along Minnesota roadways.

Report 2021-14

BRIDGES & STRUCTURES — The culmination of three previous projects investigating the use of drones, or unmanned aircraft systems (UAS), in bridge inspections, this project followed the implementation of UAS into the field to be used in the official inspections of MnDOT bridges located across the state. Investigators selected appropriate bridges and rigorously documented the inspections. The UAS models performed admirably, resulting in high-quality data obtained with fewer personnel in far less time. The usual hazards of bridge inspection, such as inspectors using ropes and climbing gear or under-bridge inspection vehicles to examine beneath decks, were avoided. MnDOT has acquired 33 new UAS that will be used statewide.

Report 2021-13

POLICY & PLANNING — Within MnDOT’s pavement management system, the condition of some pavement segments had been rated poor for longer than five years. Ride quality index ratings are calculated in part using data acquired through pavement roughness measures. Researchers investigated these pavement segments throughout MnDOT’s eight regional districts and discovered that most of them were not in poor condition at all. Instead, anomalies in the segments, such as bridge and railroad crossing approaches, manhole covers or other urban characteristics, conveyed the impression of a rough ride but were not indicative of true pavement condition. Additional data to effectively assess and express these pavement segments’ true condition will be added to MnDOT’s system.

Report 2021-16

TRAFFIC & SAFETY — Drivers who unintentionally drift out of their lanes or run off the road cause more than half of the fatal crashes on American roadways. Lane departure warning systems can reduce that statistic considerably, but currently they are costly additions to vehicles. In this project, researchers enhanced an inexpensive in-vehicle lane departure warning system that uses standard GPS data rather than more expensive, high-level GPS or cameras that are used currently in luxury cars. With an improved algorithm to estimate a vehicle’s lateral position accurately on roadways, researchers are moving toward the implementation stage: an inexpensive and accessible commercial product that can greatly improve driver safety.

Report 2021-17

MAINTENANCE — Working with the public works staff in Edina, Minnesota, researchers collected deicing data from agency trucks during winter road maintenance operations. They correlated salt usage with data they collected indicating the amount of chloride showing up in meltwater flows from the roadways. Maintenance staff could compare their salt usage during particular events with increases of chlorides in runoff and adjust their deicing operations accordingly. This adaptive management approach—constantly checking the effects of actions and making adjustments—is one way that local agencies may be able to more effectively reduce the amount of chlorides entering the environment and still achieve satisfactory winter traffic mobility. Researchers created an adaptive management manual for deicing and a spreadsheet calculator to help agency staff improve their deicing operations.

Report 2021-07

MATERIALS & CONSTRUCTION — MnDOT assesses pavement thickness to select the best methods for maintaining asphalt roadways. Historically, the agency has extracted pavement core samples to determine thickness—an expensive, destructive process that gathers limited data specific to the area and requires immediate repair of the site. Researchers investigated the use of 3D ground-penetrating radar (GPR) as a means to obtain better and larger data sets about pavement thickness. An array of up to 121 transmitting and receiving antenna pairs attached to a van can gather data at traffic speed. Data is then loaded into a new software tool for complex calculations resulting in pavement thickness data. When put to use, this process will save time and money, reducing the need for core extraction as a data gathering process for pavement maintenance.

Report 2021-19

SAFETY — MnDOT maintains nearly 400 dynamic message signs (DMS) along the state’s highways. The Regional Transportation Management Center displays real-time messages to warn motorists of congestion, roadwork or an incident ahead that could be hazardous or cause a delay. MnDOT has used DMS sparingly for severe weather messages to avoid overuse. To make winter road weather alerts most effective, researchers developed a software interface to acquire weather alerts from the National Weather Service’s system and translate them into text messages for DMS. The system selects the appropriate DMS locations and posts the alert message until it expires. Operators can return to manually posting or removing alerts at any time. MnDOT intends to begin using this system for blizzard and snow squall alerts. The automatic option for DMS messages will enhance the timeliness and accuracy of DMS alerts for severe weather and allow RTMC operators to attend to other work.

Report 2021-RTMC-1

Clear Roads, a MnDOT-led national research consortium focused on rigorous testing of winter maintenance materials, equipment and methods, selected seven new research projects for 2021 funding.

Clear Roads