Municipalities in Minnesota continuously search for the most effective ways to reduce unsafe speeds. A recent study looked at the effect of speed limit changes on vehicle speeds absent other changes. Researchers worked with the City of St. Louis Park, which implemented a citywide change in speed limits after a 2019 statutory change that allows municipalities to set speed limits for city-owned roads without prior approval. Evaluating speeds before and after the posted speed limit changes revealed considerable variability among locations and no clear effect on driving speeds. Noting that driving is a habitual behavior, researchers suggested a driver’s adaptation to a lower speed limit may happen over longer time in the absence of physical roadway changes or strict speed enforcement.

Longitudinal joints, created when lanes are paved sequentially, often need significant maintenance as the joints crack or deteriorate. While materials, construction methods and other factors may cause joint deterioration, insufficient pavement density is primarily responsible for weak joints, and measuring density has not traditionally been a widespread practice. New research provides best management practices for joint construction and quick, nondestructive methods for measuring pavement density during construction that will support local agencies in laying longer-lasting pavement.

Work zone flaggers have a dangerous job as drivers may not heed temporary traffic directions. Digital smart signs equipped with sensors and controlled remotely by workers have been developed and tested in work zones but have had varying levels of success due to operational complexities, size and cost. The LRRB wanted to develop a portable, easy-to-use system that would alert both drivers and workers of a vehicle’s unsafe approach. The system also needed to account for the needs of the flaggers. Researchers developed a cost-effective system that tracks an oncoming vehicle’s trajectory, warns workers of an unsafe intrusion and alerts drivers to slow or stop. A follow-up pilot study is underway to further modify the flagger system to allow for remote operation. Researchers will focus on road worker acceptance and determine if the driver behavior in simulations extends to real-life settings.

City of Rochester public works staff designed a cost-effective fix that makes dispensing liquid salt brine more efficient

The City of Rochester public works department identified a problem with the brine system they were using to dispense liquid salt brine to deice winter roads. It happens when the brine level in a truck’s side-mounted saddle tanks falls below the halfway point. The liquid sloshes around in the saddle tanks, particularly when the truck is traveling up or down a hill, causing the system pump to draw in air and inducing a controller error, which requires a controller reset before resuming brine distribution.

Staff researched solutions and ultimately modified the brine system by adding a "nurse" tank positioned lower on the truck than the saddle tanks and directly connected to the system pump. Gravity ensures that the saddle tanks drain into the nurse tank to keep it full, which in turn eliminates problems caused by sloshing or steep inclines. Plow operators using the modified brine tank system no longer need to reset the brine controller, making their job more efficient and less frustrating.

The department received a $5,000 grant through the Local OPERA Program to develop their solution. The OPERA program is sponsored by the Minnesota Local Road Research Board and administered by Minnesota LTAP. Learn more about the OPERA program.

This month, we're saying goodbye to three LRRB board members who've completed their terms of service. Jim Foldesi, St. Louis County, joined the LRRB in 2016 and has served as board chair since 2020. Paul Oehme, City of Lakeville, has served on the LRRB since 2015. Steve Bot, City of St. Michael, has served on the Research Implementation Committee (RIC) since 2016. We thank each of you for your leadership and dedication in service to Minnesota's local agencies and wish you well on all your endeavors! Photo: (LtoR) Jim Foldesi, Paul Oehme, Steve Bot.

Have you shared a research idea with the LRRB at a fall Pre-Screening meeting? You can go to the LRRB website and check the status of your idea on the LRRB Research Idea Tracker, which shows the status of ideas submitted over the past year. Statuses include:

• New LRRB Project: Idea has been selected and is in process of starting or being contracted.
• Under Consideration: Idea received high number of votes and is going through the LRRB process to identify potential researcher and if research can be done economically.
• Lower Priority: Idea did not receive enough votes to be considered for funding by the LRRB and RIC (i.e. not within the top 25 projects); these ideas will be sent to cities and counties to consider for “re-nominating” during next cycle.
• Existing: Idea was addressed in previous (or is being addressed by current ongoing) research project.
• N/A: Idea was being addressed elsewhere (i.e. previous research, via State Aid) and/or was deemed not research type issue.

We need your input!  The research team for the LRRB project, Pedestrian Safety and Accessibility Best Practices for Channelized Right Turn Lanes, seeks to identify local agencies' practices, policies, and guidelines related to improving pedestrian and bicyclist safety at signalized intersections with channelized right turn lanes.  

Your feedback will aid their understanding of existing practices and strategies in place in jurisdictions across Minnesota. Full instructions are provided on the survey page.  Please complete the survey by Friday, Dec. 22. We greatly appreciate your responses!