The development at the intersection of Franklin and Lyndale Avenues in Minneapolis has gotten a lot of attention, but primarily because of buildings proposed at the corners, to replace under-developed buildings at this highly accessible, emerging locale.
The intersection itself has gotten little consideration. It is an at-grade 4-way traffic signal. However, Franklin Avenue finds itself in a valley at Lyndale, such that a 3-dimensional option presents itself.
Urbanists are often aghast at the notion of highway overpasses in cities, and certainly most have been done poorly with no respect for urban form. But that is no reason to throw out the concept altogether.
Using my extensive computer drafting skills, I present two diagrams. The Plan view (from above) and Side view (facing west) illustrate a concept in cartoon fashion. These are, as they say, not-to-scale and obviously not engineering diagrams.
The top diagram shows how the middle two lanes on Franklin Avenue (the left lanes Eastbound and Westbound) bridge over Lyndale Avenue (the blue bar represents the bridge). Since there are already two lanes, additional land required is only for bridge barriers, and hopefully that is minimal. Lanes can be narrowed as necessary.
This does several things. It gets cross-traffic on Franklin (going to or from Hennepin mostly) off of Lyndale. This reduces pressure on Lyndale itself, reduces traffic delay, reduces pedestrian delay, reduces bicyclist delay, reduces pollution at the intersection, reduces street crossing times for pedestrians on Lyndale going North or South (there are two fewer lanes to cross). A median boulevard could be added to Lyndale (the green bars).
The intersection of Franklin and Lyndale thus becomes an urban diamond.
There would be an option to eliminate some or all left turn movements as well, and make Lyndale more Boulevard like with no at-grade cross traffic from Franklin. The intersection could be just right-in/right-out for motor vehicles. Pedestrians could be given a Hawk signal if they wanted to cross Lyndale, with a median refuge island. The purple bar shows this region.
The downside is making it more difficult to access businesses on Lyndale (e.g. The Wedge Co-op) which are already difficult to access by car.
But even if there were left-turns allowed, traffic would be much lighter at the intersection.
The second diagram shows a Side view / cross-section. The idea here is not the particular architecture or building heights, but to illustrate that just because there is a 2 lane overpass, the underside of the bridge can have a pedestrian serving business (that is no more than 26 feet wide). (This need not be a cafe, but in every urban rendering I have ever seen, there are cafes, so there must be a reason).
Most intersections are not situated such that 3-dimensions is such a natural solution, but there are some, and we should consider the possibilities.
Full disclosure: I don’t live very near there, and only use the intersection occasionally as a motorist.
Cross-posted at streets.mn