The diverging diamond interchange efficiently serves motor vehicles, but serves bicyclists and pedestrians poorly.
While I intend to write about bicycling and walking in rural Missouri even though I'm now living in Columbia, realistically I'll stray into Columbia territory now and then. I want to try to keep it relevant to bicycling and walking in rural Missouri when that happens. But I have to admit that today's post isn't relevant to rural Missouri, unless the diverging diamond interchange really takes off and we start seeing it everywhere.
The new diverging diamond interchange at I-70 and Stadium Blvd is a strange creature that has to be seen to be understood. Actually, after biking through it, I still don't entirely understand it, but it seems to work smoothly, and if you are getting on or off the interstate the left turns flow easily (of course, I didn't get on the interstate on my bicycle). It's a bit creepy because the lanes swap as you drive over the interstate, so that you are driving on the left side of the road instead of the right. But it all happens naturally and smoothly.
I took a traffic lane and biked through it. I stayed in the right lane. I had no problems with it, other than that it felt really odd to be in the far right lane and at the same time in the innermost lane. Most bicyclists would not be comfortable in the amount of traffic typically seen on Stadium Blvd, and in fact I ordinarily don't bike on the north end of that street myself. (The south part has bike lanes and wide shoulders.) If I need to visit that side of town, I know a secret way around.
Next I tried out the pedestrian crossing, the more likely path most bicyclists would take if they had to cross over the interstate right there. As a pedestrian, I crossed half the street and ended up in the middle of the road, where a long, narrow corridor guided me across the bridge and over the interstate. On the other side of the bridge, I crossed back to the edge of the road.
I thought there is no way two wheelchairs could pass each other in that narrow corridor and there is no place in that 1/10th mile stretch for one to pull over and let the other pass, should they happen to meet. I measured the width of the corridor with my bike, then later measured my bike. My bike is longer than I thought--it is 5 1/2 feet, which makes the corridor 6 feet wide. That is wide enough for two wheelchairs to pass each other.
While the pedestrian crossing is not designed for bicyclists, there are no bike lanes marked and I believe most bicyclists unfortunate enough to be crossing on this bridge will use the pedestrian walkway. At 6 feet wide, it is too narrow for two bicyclists to pass: the Urban Bikeway Design Guide specifies 12 feet for this purpose, with an absolute minimum of 8 feet.
My conclusion is the diverging diamond interchange is all right for motor vehicles, but only the most desperate bicyclists and pedestrians will use it. For a town that has the best bike/ped facilities in the state, this new facility serves bicyclists and pedestrians poorly.