In a presentation for the Rutherford Chamber of Commerce on March 17, Michelle Nickerson, civil engineering manager for the Tennessee Department of Transportation, explained the current $45.8 million phase—a portion of the total $109.5 million budgeted for the project—would reduce delays due to crashes and centrally control dynamic messaging systems to give drivers advance warning of delays ahead.
“We are excited about the I-24 Smart Corridor project, because we believe it will help improve reliability and safety along I-24,” said Patrick Cammack, Rutherford Chamber of Commerce executive vice president of economic development. “...As prospective residents and businesses evaluate our community and region, seeing this public investment in infrastructure is more important than ever, especially in the midst of our strong projected growth.”
Work began in early April to install 67 overhead gantries every half mile in both directions within a 28-mile stretch from Exit 81 at US 231/Church Street in Murfreesboro to Exit 53 at I-440 in Nashville. Lane closures for overnight construction along that stretch are expected to last until November, according to TDOT.
Further widening of the interstate is not financially feasible and does not permanently manage growing traffic, according to TDOT.
By late 2022, TDOT plans to activate the signs on the gantries giving notice of lane closures, speed limit changes and offering drivers alternative routes around backups, said Rebekah Hammonds, TDOT community relations officer for District 3, which includes Murfreesboro.
“These improvements will not necessarily improve travel times, but they will make them more reliable,” Hammonds said. “This makes your commute more like a train schedule, where it runs, ‘on-time’ more often but does not necessarily make the train any faster.”
The I-24 project is intended to address congestion in the area, where traffic volumes have increased 60% in the Murfreesboro-Rutherford County stretches since 2005, according to TDOT.
Included in the first phase of the project, which started in 2018 and finished in 2021, were extensions of on- and off-ramps, a change intended to ease speeding up and slowing down on and off the interstate with fewer crashes, according to Hammonds.
The addition of emergency pull-off areas provide a safe median for disabled vehicles to pull out of traffic if possible, reducing the potential to block active lanes.
A TDOT analysis of 2015 congestion data attributed 55% of traffic congestion to heavier traffic volume and 27% to traffic incidents such as accidents or breakdowns.
“This helps to prevent the phenomenon of drivers tapping their brakes, which causes something called ‘phantom traffic jam,’ which is a slowdown of traffic not caused by bottlenecks or a traffic incident,” Hammond said.
Integrated corridor management
The new signage displayed on the overhead gantry systems will include red x’s to indicate lane closures, yellow arrows to communicate drivers should exit a closed lane and green ones to indicate a lane is clear. To prepare drivers for the use of this new signage, TDOT will produce videos about their meaning, according to Nickerson.
With the extra information, Hammonds said, drivers should be able to respond appropriately to avoid accidents or follow a suggested detour.
“The Integrated Corridor Management strategies will reduce the overall incident durations, which leads to shorter queues, lowering the probability of secondary crashes,” Hammonds said.
By the end of the year, TDOT engineers and technicians will also be gathering data regularly to use vehicle counts, average speeds and other data to find areas for improvement, Hammonds said.
“Extensive data will need to be collected to definitively assess the improvements,” Hammonds said. “In future years, the monthly, quarterly and annual data will be compared to quantify the improvements.”
Later in the year, TDOT will hire a new analyst to manage the corridor from the state’s Traffic Control Center to oversee the system, according to TDOT.
Around the end of 2022, further communication upgrades will allow TDOT to add the dynamic messaging signs on Murfreesboro Road to provide updates about I-24 traffic on the route, Hammonds said.
That phase, scheduled to wrap up next year, would also install ramp-metering equipment to control the pace of vehicles exiting and entering the highway.
Murfreesboro Transportation Director Jim Kerr said the cities of La Vergne, Smyrna, Murfreesboro and Nashville will be able to veto TDOT’s requested signal timing adjustments based on local road conditions.
“At least with the Smart Corridor project we will have some mitigation and notice if we choose to deploy a diversion,” Kerr said.
With traffic projected to keep growing with the population, Kerr said using technology will be less costly than widening.
“Investing in traffic signal technology is an extremely good investment because it’s pennies on the dollar to major road projects,” Kerr said. “Don’t get me wrong, you need to do both, but you have to maximize what you get from your roadway system.”