Here are some details on the roundabouts that the 3-Plus for Russell Street plan proposes:
Russell/3rd, Russell/Mount: 120′ ICD (inscribed circle diameter- as
measured curb to curb through the circle), single circulating lane, 10′ sidewalks around the roundabout (separated from the roadway by a boulevard: 1′ to 8′ depending on space availability).
Example:
http://www.roundabouts.net/pics/roundabouts/roundabouts_grandjunction_small.jpg
The above example is very good in showing how a bike lane is treated at modern single lane roundabouts- a cyclist either takes the middle of the lane, or uses the ramp up onto a wide sidewalk (10′ is best, but can be 7′ or 8′ if space is constrained). The Missoula roundabout at England Blvd and Connery Way is about 120′ for reference.
Russell/5th: 104′ ICD, single circulating lane, same sidewalk issues as above. Note: May have to limit trucks to WB 50 (common in other communities) instead of allowing WB 67 (Walmart sized truck), or make the truck apron larger, or make the roundabout fully mountable.
Example:
http://www.roundabouts.net/pics/roundabouts/roundabouts_montpelier_small.jpg
The above example is a 3-leg roundabout, but it would be applicable to Russell/5th since 5th has a leg that is one way. Also, there is growing advocacy/support for 5th and 6th to become one lane for motorized traffic, and one wide bike lane. Traffic volumes, now and into the future, allow this change to easily happen. That change would facilitate an even bigger shift to cycling (the cycling system would be more complete, safer and more accessible), thus helping bring down future motorized traffic volumes on Russell.
Russell/Wyoming: 110′ to 120′ ICD
(Note: The 4 lane to 3 lane transition is being proposed for mid-block, between Montana and Wyoming. Mid-block merging and diverging is generally a safer and more fluid way to add/drop lanes than at an intersection. While people complain about the W. Broadway lane drops at the intersections, we do not hear complaints about two lanes merging to one on Russell near Mount, on Brooks just north of Mount, or on Broadway east of Van Buren, for example.)
Russell/7th and Russell/11th: 90′ ICD, or change to left turn pocket. The
concern is that we may not want too many roundabouts in one corridor. Yet, since 7th to 11th on Russell is the tightest ROW, left turns will have to be prohibited or discouraged, thus making a roundabout fairly desirable since ‘right in right out’ is easily done when a motorist can take a right, go the next roundabout, do a u turn, come back and take another right. This item needs more community discussion.
Good example of a modern single lane roundabout with an 88′ ICD:
http://lh4.ggpht.com/_xmdwlenXUv0/RbvFpeEPOcI/AAAAAAAAAAg/CXmUWFfjmZc/DSC00006.JPG
The capacity of single lane roundabout at Russell/3rd: 25,000 a day, or 2,500 per hour. The last count (9/9/08) at rush hour (4:30pm to 5:30pm) showed 2,122 cars passing through (right, straight, left: all legs). Thus a single lane roundabout could handle about 15.12% more cars - at rush hour, under current context.
Yet more people are cycling, walking and taking transit and that trend is expected to grow. We also know other TDM measures, like ones Missoula in Motion is promoting and working on, are very successful and will likely become even more successful. Simply shifting 100 cars out of rush hour has a huge positive effect. Making Russell very ‘human-scale’, as a 3-lane instead of 5-lane, further encourages walking, cycling and transit.
Not tearing down any houses keeps people in situations that make walking, cycling and transit very feasible.
Rising fuel costs, peak oil, climate change, local air quality, and Envision Missoula results are reasons to refute the 20 year projection of 37.7% more traffic on Russell. In the Envision report, widening roads was #22 on the list of ’solutions’, as cited by the public. More walking, more cycling, and more transit all scored higher on the list.
A couple more notes:
Research shows that lots of pedestrians does not have much of an effect on vehicle capacity, especially on roundabouts nearing capacity. When cars are going slow, and waiting for gaps, pedestrians can easily ‘move through’ without delaying vehicles significantly. The effect is similar, but not as much so, for cyclists. It is estimated, based on conversations with engineers in Bend, Oregon, that half the cyclists will ‘take the lane’ while half the cyclists will use the ramp onto the sidewalk. A person on a bike at the ped crosswalk will not have the right of way. A person who dismounts from their bike at the ped crosswalk will have the right of way.
The best solution would include 3-laning the rest of Russell, south to Brooks street. This would allow bike lanes and easier ped crossings without losing motor vehicle capacity. The best solution also looks city-wide and considers system wide improvements like trail connections, bike lane completion, 15 minute bus service, integrating the future return of Amtrak to the Circle Square Depo, more cycling services like Free Cycles (already being planned) and bike stations (in planning too).
For more technical information on the 3-Plus for Russell Street proposal, contact us.
Bob Giordano
Missoula Institute for Sustainable Transportation
mist [at] strans [dot] org
406.880.6834
