Bicyclist. It is a word that can incite frustration in the minds of both drivers and traffic engineers alike. But, let’s face it: bicycles are good for the environment, they are cost-effective, they are good for our collective and individual health, and the presence of cyclists within a community creates a positive image that says we care about the environment, we are health-aware, and we feel safe enough in the community to ride our bikes down these city streets. With an increasing number studies showing that bicycle traffic increases in areas that have dedicated infrastructure in place for cyclists, it’s no wonder why we are starting to see an increase in requests for multimodal traffic solutions.
Case Study: Louisiana Ave. & 28th St., St. Louis Park, MN
The City of St. Louis Park, Minnesota has been very diligent in reviewing their infrastructure and ensuring their transportation planning process is keeping up with the growing needs of the community. Over the past 10 years, we have worked with them on many projects, particularly as they have started to focus on multimodal traffic solutions. Most recently, they asked us to look at the intersection of Louisiana Ave. and 28th St. to see if removing the left turn lane on 28th St. would be a viable option to provide space for a bike lane. (This case study was a featured webinar for Traffic Corner Tuesday. Check out the recording)
Louisiana Ave. is a minor arterial, two-way road that carries roughly 17,200 vehicles per day, whereas 28th Street is a neighborhood collector carrying 2,900 vehicles per day. The city was considering 28th Street into a bicycling corridor.
Step 1: Consider Options
Our first course of action, before getting to deep into the analysis of the site, was to put pencil to paper and sketch out some options.
Our first option was to reduce the lane width to 10.5’ lanes in each direction on 28th St., add a 5.0’ bike lane, and a 7.0’ parking lane. We recognize that a 10.5’ lane has the potential to get tight, but we felt comfortable with this option because – apart from the occasional school bus and garbage truck – there are not a lot of large vehicles traveling on this road.
Our second option was to create a bike lane on either side of the road, and we used variable lane widths to determine that it would be feasible to have two 5.5-6.0’ bike lanes with two 10.5-11.0’ drive lanes on this street.
The final option was to eliminate the variable space from option 2 to create delineators for the protection of the cyclists. Studies have shown that bicycle traffic increases and related injuries decrease when there are protected lanes for cyclists to travel in. Unfortunately, this option creates a challenge during the winter months, as snow removal becomes a necessary consideration, but that is certainly not a deal-breaker for this scenario.
Step 2: Analysis
After sketching out three viable options for creating bike lanes on 28th St., was to run analysis using Vistro.
Using the existing timing, turn movement and volumes to determine that the intersection was operating at Level of Service D. When we factored in an increase in bicycle traffic, taking out the left turn lane and some timing adjustments, we found the Level of Service would stay roughly the same.
When we looked at queuing, however, we saw some red flags that were cause for concern. By forcing the right turns to mix with the left turns, we saw a 2x-3x increase in our 50th percentile queue. With only 260 feet of roadway before the intersection to work with, the increase in queue was a considerable concern for us.
While we are typically very open to repurposing space and pushing the boundaries in an effort to keep traffic solutions current and accommodate multimodality, the increase in queue and the safety implications were just too significant for us to ignore.
We have provided the city with our findings, and they are currently exploring ways to validate the findings via temporary trials. As we all know, software and modelling can be excellent tools for analysis, but experiments can provide us with real data that we just can’t get in any other way. We look forward to seeing the results of these experiments and will keep you posted!
Are you interested in learning more about bike lanes? Check out our free Traffic Corner Tuesday webinar Removing a Left Turn Lane to Provide a Bike Lane. In this episode, Mike Spack and Bryant Ficek walk through the case study that was basis for this article.
Or signup for our Traffic Corner Tuesday webinar series. Each webinar is 30-minutes of free traffic engineering best practices from industry experts.