How to Detour Around the 2025 I-170 Overpass Closure at I-270

On June 20, 2025, the Missouri Department of Transportation closed off the eastbound ramp on Interstate 270 leading to Interstate 170. The reason, according to MoDOT, is to replace the bridge over Pershall Road, which MoDOT says was built in 1978 and is “being replaced due to age and a substandard substructure.”

If you’ve lived in St. Louis for a while, you might remember MoDOT doing a reconstruction of the 270 to 170 interchange back in the early 2000s, where the exits from 270 East to 170 South were moved from the left side of 270 to the right side. That job took a long time and was a major headache for commuters, which makes it unfortunate that MoDOT didn’t replace this bridge at the time.

Nevertheless, I-170 South from I-270 East will be closed from June 21, 2025 to sometime in September 2025. If you’re heading west to 170, you’re not affected, but if you’re trying to get into 170 heading north and east on 270, you need a new route.

There are technically a number of options, including heading down to 70 and taking that to 170 or taking 270 down to 64, although those options can add miles, drive time, and other potential interchange and / or construction headaches. They may also not fit your destination.

Instead, I want to focus on the two main options: the official one given by MoDOT and another possible one that was used by motorists during the early 2000s construction.

Option 1: Washington / Elizabeth U-Turn Lane

The official MoDOT detour has drivers overshooting 170, getting off at Washington / Elizabeth, taking a U-turn lane, and then getting back on 270. The detour involves no stop lights.

It’s a fairly simple route. You drive pass the Hanley Road exit and then get into the Washington / Elizabeth exit, which is right after to the exit for New Florissant.

You stay on the left lane of Pershall Road, and as you approach Washington and Elizabeth you’ll notice an emerging U-turn lane.

Drivers can then follow that U-turn lane straight around and onto Dunn Road, the north outer road.

You’ll loop around the U-turn, and in short order be headed toward 270 West. There is no stop light for the U-turn, although it’s good to be aware of traffic coming in from your right.

You don’t even need to make any lane changes at this point, as the U-turn lane turns into 270 West, which in turn turns into 170 South.

Option 2: Hanley to 170

This is not the MoDOT detour, but it is an option. In the early 2000s, it was the only option, because the U-turn ramp at Washington / Elizabeth was only completed in the 2020s as part of the massive 270 construction project. It’s technically fewer miles than the U-turn ramp, but, unlike the U-turn ramp, has intersections, stop lights, and people turning on and off of side roads. In addition, it seems Google Maps defaults to this option, which may make it more trafficked by people trying to get onto 170.

You start by turning onto Hanley Road headed south. You then proceed a ways down Hanley, past Latty Ave., until you see the Hanley Road Spur, which runs by a QuickTrip gas station.

The left two lanes on the spur flow directly into 170, with the far left lane eventually ending and merging into the second from the left lane.

Our Thoughts

While no one is a fan of the 170 ramp closure, there are ways around it. Google Maps is likely to route people through Hanley Road, and many people who were around for the 170 overpass reconstruction in the early 2000s might do the same, since that was the only real option in those days. With the construction of the new U-turn ramp at Washington / Elizabeth, though, drivers now have another choice. MoDOT’s official detour is that U-turn ramp.

It’s our view that, in most cases, the U-turn ramp is the better option. Yes, it’s more miles, but it’s also free of stop lights thanks to the design of the U-turn ramp. Hanley can and will get congested, thanks to the fact that it’s a city road with stop lights. Hanley might be preferable during 270 rush hour slowdowns or if there is an accident on 270 between 170 and Washington / Elizabeth, but in most cases we think the U-turn is easier, even during busier times. Our own video above was taken at 5 p.m. on a weekday.

Regardless of which you like better, I think we all can agree that it will be nice when the 170 ramp reopens in the fall of 2025.