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TDOT upgrades I-24 as high-tech highway

JASON M. REYNOLDS

Jan. 22, 2020

TDOT is engaged in a multi-year process of upgrading Interstate 24 and side roads to create a “SMART Corridor.”

The corridor in Rutherford and Davidson counties will feature three phases of improvements like extensions to acceleration and deceleration ramps and pull-off areas for vehicle accidents, said Brad Freeze, director of the Traffic Operations Division for the Tennessee Department of Transportation.

Phase One is under way, Freeze said. Phase Two’s contract was awarded in October and will start soon, possibly in February.

TDOT’s website shows Phase Three should be finished in the winter of 2023. Phase One cost $19.3 million, and Phase Two cost $45.8 million, said Kathryn Schulte, TDOT community relations officer. She said she did not have an estimate for the cost of the final phase.

In addition to connector roads, the project includes about 28 miles along I-24, from Exit 53 (I-440) in Metro Nashville to Exit 81 (SR 10/U.S. 231) in Murfreesboro, according to TDOT’s website. It also includes about 28.5 miles along SR-1 (Murfreesboro Road), from I-24 in Metro Nashville to SR 10/U.S. 231 in Murfreesboro.

Some work will not be too visible, such as installing traffic signal controllers and fiber-optic infrastructure, Freeze said.

Visible work in Phase One will include the creation of 14 “refuge” areas in which cars involved in an incident can wait for help to provide a buffer from traffic and eliminate the need for a vehicle sitting on the shoulder, Freeze said. TDOT will create the refuges based on locations where incidents have historically happened the most.

Pedestal-mounted signs will be mounted at 19 locations on the shoulders at a frequency of about every three miles, Freeze said. These are in addition to the larger signs that already are mounted over multiple lanes. The goal is to provide even more information to drivers.

Ramp extensions in Phase One will increase the speed at which a car can merge into traffic or decelerate while exiting, Freeze said.

Phase Two will include overhead lane control signals so each lane will have a “dynamic” sign above it to provide lane-by-lane information, Freeze said. If there is a lane closure a mile ahead, this sign can say so. Current signs are placed every three miles, but sometimes if TDOT provides lane closure information that far out, drivers may move over sooner than necessary and clog traffic. These new signals can provide “speed control” and slow traffic down just enough to better manage the flow and avoid gridlock, he said.

In Phase Two, the signal controller upgrades will include 146 signal locations like on Murfreesboro Road heading into Nashville and all cross streets to State Route 1 (Northwest Broad Street), Freeze said.

TDOT is preparing for new signal timing plans in which once an incident happens, officials can divert traffic to arterial side streets if needed and push the signals to change in a progression that would keep traffic flowing and get drivers around the incidents and perhaps back onto the freeway, Freeze said. Planners are basically looking at I-24 and the arterials as one system.

TDOT will be able to coordinate with cities, he said, and will not make signal changes without their approval. The end of Phase Three will allow the system to be as close as possible to being automated.

Another feature will include “incentivized towing,” Freeze said. This means that during certain conditions, such as peak travel times, if a tractor-trailer rolls over and could cause a long-term closure, officials could pay a towing company an incentive if it can clear the highway in fewer than 90 minutes. This happens now in other states like Georgia.

Phase Three will include ramp “metering,” which is done in other states but is new to Tennessee, Freeze said. This system uses a signal to space out traffic attempting to enter the interstate from an on-ramp.

Another change will be to allow transit buses to drive on the shoulders when interstate speed drops below a certain threshold and jump around the problem area, Freeze said.