Getting your Trinity Audio player ready...

The Austin City Council on Monday night agreed to move forward out of its work session a plan for an upcoming detour resulting from the continued Interstate 90 bridge construction project.

According to City Engineer Steven Lang, work is slated to begin on the third bridge of the project — Fourth Street NW — in September and is expected to take a full year to complete.

During that time traffic from both the north and south will not be able to cross Interstate 90, forcing a diversion to other streets. The brunt of that traffic is expected to shift to 14th Street NW.

This shift in traffic flows is also expected to create a congested condition along that route and likely branching off into other avenues and streets.

On 14th Street alone, traffic currently sees an average vehicle per day (vpd) volume of 13,000 vpd while Fourth Street NW sees an average of 12,364 vpd. When the detour takes effect it will greatly increase the volume on 14th to potentially 28,100 vpd.

“We are concerned about the volume of traffic diverted to 14th Street,” Lang told the council. “Once they all get to 14th Street, it’s going to impact our intersection control we have on 14th Street.”

At the same time, Lang said that the detour is likely to affect businesses north of I-90 on 14th as well as homes and businesses to the south. It will also have an effect on eastbound exiting traffic from I-90.

The plan approved to be moved forward to a regular meeting Monday night would replace the four-way stops at Fourth Avenue and 14th Street NW and Eighth Avenue and 14th Street NW with temporary signals.

In a memo to council, Lang explained that the signal lights will allow the intersection to function more effectively by allowing large groups of vehicles to move through the intersection at one time without each vehicle needing to stop.

The signals will also allow for gaps in traffic flow making it easier to merge or go across for vehicles coming off the avenues onto 14th Street.

Cost for the temporary signal lights over the one year period comes to an estimated $240,000 or $10,000 per month per intersection.

At the same time, Lang said this will open two more conversations later down the line. One is a reversal of considerations when it’s the 14th Street NW bridge’s turn for replacement, which will reverse the flow of detoured traffic to Fourth Street NW.

In turn, a separate conversation will likely need to happen regarding increased traffic flows down side avenues in Austin.

“It’s going to lead to talk of uncontrolled intersections in the northwest part of Austin,” Lang said. “It’s going to come to light because of this.”