The Local Road Research Board has brought important developments to transportation engineers throughout Minnesota for more than 50 years. These advances range from new ways to determine pavement strength to innovative methods for engaging the public.
Today, the LRRB remains true to its important mission: supporting and sharing the latest transportation research applications with the state's city and county engineers.
How About a Roundabout?
The Minnesota Experience and a Minnesota Guide
A modern roundabout is a circular intersection where traffic flows around a center island.
Today, roundabouts can be alternatives to traffic signals and stop signs to control traffic. In many cases, they have several
advantages over signals and stop signs, including:
Fewer injury crashes and fatalities
Increased pedestrian safety
Less vehicle delay and pollution
Roundabouts, like all intersections, undergo thorough analysis prior to implementation to determine if it is the appropriate solution. MnDOT has more information concerning roundabouts located on their Roundabouts page.
Today, roadways are designed using engineering factors that establish the quantity, type and thickness of material that
needs to be used to balance vehicle loads and roadway use.
Among other factors, current pavement design considers the amount, type and weight of the traffic using the road. This data is used to calculate an ESAL (equivalent single-axle load) factor; this factor is a way of measuring the impact that a vehicle will have on a pavement.
Pavements can be viewed as a "consumable" and are designed to carry an estimated number of ESALs over their design life. As each vehicle passes over a pavement, a portion of its life (the vehicle's ESAL factor) is consumed. Eventually, a pavement's life is expended, and it needs to be reconstructed.
To Pave or Not to Pave?
Making Informed Decisions on When to Upgrade a Gravel Road
Until the mid-1990s, almost all cold-in-place recycling involved the use of emulsions. In recent years, countries and states began to turn instead to foamed or expanded asphalt. Effective with cold-in-place recycling and full depth reclamation methods, foamed asphalt helps add strength and moisture resistance to the remaining pavement materials.
The Minnesota Local Road Research Board sponsored a recent research project to assess the recycled pavements that use foamed asphalt, evaluate such projects in Minnesota and develop design guidelines. The project confirmed that all cold-in-place recycling sections with foamed asphalt are performing very well to date and that transverse cracking and rutting appears to be reduced by the use of foamed asphalt cold-in-place recycling rehabilitation techniques.