4-to-3 Lane Conversions

The study involved four phases: feasibility screening; benefit analysis; detailed analysis and concept development for segments identified for further study; and prioritized implementation plan development. The study is being used to guide long-term planning for maintenance, funding and reconstruction. Full study materials and information about previous 4-to-3 conversions in the county are available at ramseycounty.us/4to3Conversions.

 The study looked at 22 different road segments to determine whether a lane reduction would have a positive impact. The segments vary in length from 0.3-4 miles and represent a combined 27.5 miles of county roads, about 10% of all roads managed by the county.

All segments were first reviewed to determine the general feasibility of a successful conversion to a three-lane road. The screening examined potential items that will need to be resolved when planning a 4-to-3 lane conversion.

The screening looked at several factors:

Improved safety for all road users is the biggest benefit of a 4-to-3 lane conversion when possible. If a road doesn't have the right characteristics, a conversion can actually make safety and operations worse. All segments were scored to determine which potential conversions would have the biggest benefit, particularly for the safety of pedestrians and bicyclists. The analysis looked at five factors to determine the relative benefits of converting the segment to a three-lane road: access point density, speed, crashes per mile, pedestrian crossing volumes and bicyclist volumes.

Scores between 1-5 were assigned based on these criteria and were then equally weighted to determine an overall score. A higher score signifies higher benefit, while a lower score signifies a lower benefit.

These benefit scores helped show where a road conversion may make sense even if the technical feasibility was lower due to a higher volume of daily traffic or other factors.

Conversions typically reduce crashes because they reduce the potential crash points. Research shows a roughly 47% reduction in crashes when converting a four-lane undivided road to three lanes. Roads with a higher number of crashes per mile were given a higher score.

Conversions increase pedestrian safety by reducing the number of lanes to cross and creating opportunities for center median island space for pedestrians. Pedestrian volumes were measured using mobile device data, and volumes were based on the number of pedestrians crossing the road, not traveling along one side of the road. Scores were determined by comparing all road segments in the study against one another –the corridor with the highest volume was given a 100 and the other corridors were adjusted based on their proportion of crossings. Scores were then created to benefit points using the following scale: five points for 80-100, four points for 60-80, three points for 40-60, two points for 20-40 and one point for under 20.

Conversions increase bicyclist safety by reducing vehicle speeds and creating opportunities to add bike lanes or buffer space. Bicyclist volumes were also measured using mobile device data, and roads with a higher number of bicyclists were given a higher score. 

The same methodology used for scoring and assigning benefit points for pedestrian crossings was used for bicycle use.

Conversions typically help reduce vehicle speeds. The study looked at operational speeds compared to speed limits. Roads where motorists frequently drive faster than the posted speed limit were given a higher score.

Roads with a large number of mid-block access points benefit from conversions because turning vehicles have one less lane to cross. Roads with a higher density of access points were given a higher score.

Following the feasibility screening and benefit analysis, five Ramsey County road segments that may be more challenging to convert were selected for detailed analysis and concept development. The project team then put together a prioritized implementation plan based on technical engineering and funding needs. The final order of implementation will include and prioritize racial equity and community engagement alongside technical feasibility to continue shaping a transportation system that’s safe and efficient for everyone. 

View the prioritized implementation plan and detailed analysis documents at ramseycounty.us/4to3Conversions.