I-94 land bridge: Fewer crashes, but more severe

The state legislature is looking at spending $500 million on a “land bridge” over I-94 from Lexington Ave to the Capitol. $6.2 million has been tucked into the 2021 Tax Bill for project development of a “land bridge freeway lid over marked Interstate Highway 94 in a portion of the segment from Lexington Avenue to Rice Street in St. Paul.” As my colleague Bill Walsh explains:

It’s being built to try to right a wrong that happened 70 years ago when the highway was built through a mostly Black neighborhood. 

It is hard to see how the project will right that wrong, given that very few people living in the area now — those who will supposedly benefit — were living there seven decades ago — as were those who were supposedly harmed.

Putting that aside, what are its merits purely as a traffic project? The Lowry Tunnel in Minneapolis has a somewhat inflated reputation for being dangerous. What does the research tell us about such tunnels?

A paper that “reviews aspects of traffic safety and behavior of drivers in road tunnels based on several case studies of traffic accidents along the traffic zones of tunnel alignment” finds that:

The risk of a crash in a tunnel is reduced compared with crashes on the open road (approximately half); however, tunnel crash severity is higher.

This is so:

…especially in the event of fire due to the enclosed environment and expansion of heat and smoke. 

So there is a trade off: fewer crashes in tunnels like the one proposed, but those crashes there are tend to be more severe.

The proposed land bridge will doubtless be very expensive: given the inability of government to control the costs on projects like this, it will almost certainly end up costing far more than $500 million. The land bridge is also likely to be almost entirely pointless: you cannot right wrongs done to one group of people by rewarding another set of people. And there will be, quite possibly, costs in terms of decreased road safety from forcing interstate traffic through a two-mile-long tunnel. This project is a strong contender for the title of Golden Turkey.