A Shoulder to Drive On

SH 161 in Irving, Texas. Photo: TxDOT

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Dallas-Fort Worth Highways Demand Innovative Solutions to Alleviate Congestion.

By Nancy Mitchell, P.E.

State Highway 121 is a major highway that runs from southwest to northeast through north central Texas. It cuts across the Dallas-Fort Worth Metroplex in a wide variety of configurations, from a freeway in the urbanized areas, to a two-lane country road just outside the Metroplex.

For a 3.5-mile section between SH 183 and Glade Road in northeast Tarrant County, SH 121’s configuration changes from three general purpose lanes to two in each direction. With an average daily traffic of more than 130,000 vehicles, the bottleneck at this section causes drivers to squeeze into a tighter space. Speeds drop and gridlock ensues. In fact, it’s not uncommon for traffic to back up for several miles during peak periods.

“The congestion had reached a level where we needed a solution quickly,” said John Cordary, TxDOT Fort Worth District’s deputy district engineer.

Interim Solution

Looking north-bound toward Harwood at roadway widening. Existing asphalt shoulders have been removed. Photo: LAN

To alleviate the congestion, the Texas Department of Transportation (TxDOT) proposed an innovative traffic fix: widen the inside shoulder into a third lane for use during peak hours.

Part-time shoulder use is a common practice in some European countries and is gaining in popularity in the United States. According to the Federal Highway Administration (FHWA), there are currently more than 30 shoulder-use installations in 14 states, but many part-time shoulder use facilities utilize the right side outside shoulder.

“This is only the second time we are implementing a peak-period use shoulder lane in Texas,” said Cordary. “We knew a more permanent solution like adding capacity or reconstructing corridors would take us many years to advance through the project development process. Widening inside shoulder lanes and using them during peak hours provides an interim operational solution that we can not only implement relatively quickly, but also cost-effectively.”

Alternative Analysis

To implement this operational solution, in January 2017, TxDOT selected Lockwood, Andrews & Newnam, Inc. (LAN), a national planning, engineering and program management firm, as the lead design engineer. Maldonado-Burkett was on the project team to implement the project’s Intelligent Transportation Systems (ITS).

The existing lane consists of two,12-foot lanes; 4-foot inside shoulders; and 10-foot outside shoulders in each direction. The scope of the project includes widening inside shoulders for north and southbound SH 121, as well as widening overpass bridges at Harwood Road, Cummings Drive, Cheek-Sparger Road and FM 157. Other project features include ITS and active traffic management strategies such as closed-circuit cameras for incident detection, overhead dynamic message signs, additional lighting, emergency pull-off locations, and rapid-response tow trucks to remove stalled vehicles.

New bent construction for bridge widening at Cummings. Photo: LAN

To determine the optimal solution, LAN evaluated various alternatives for widening the section. After reviewing the alternatives, TxDOT chose additional widening for a 10-foot inside shoulder for the north-bound lanes to enhance safety for the traveling public and facilitate enforcement. The north-bound lanes have a continuous concrete traffic barrier so the added 10-foot shoulder will provide a safe place for law enforcement.  All bridges will be widened to the maximum width to the inside so TxDOT will not have to widen again on the inside, maintaining the structural integrity of the bridges. Following TxDOT’s decision, in September 2018, the project was let and Austin Bridge & Road, Inc. was awarded the contract for $17.4 million.

Lessons Learned

In 2015, TxDOT implemented a similar solution on a three-mile stretch of State Highway 161 in Irving. This project also used the existing highway shoulder to provide one additional travel lane in each direction during selected travel times. This project was the first of its kind in Texas, and the solution significantly alleviated the congestion in that corridor. However, there were also some challenges after this implementation. TxDOT applied two important lessons learned from that project in the SH 121 project.

The first was the enforcement mechanism. After the SH 161 project was implemented, some commuters started driving on the shoulder lanes at all hours. This meant that if a police officer pulled someone over and stopped the car on that lane, it would affect the rest of the commuters on that lane. Consequently, enforcement became an issue. To deal with this concern, TxDOT and the project team chose to add the extra 10 feet of pavement to the north-bound lanes.  In effect, the north-bound lanes would have a 22-foot shoulder during non-peak periods and a 10-foot shoulder during peak periods. This ensured that police officers would be able to use that extra shoulder space when not in operation, and for other emergency situations.

The second important takeaway from the previous project was dynamic operations. On the SH 161 project, the shoulder lanes were open during peak periods only from 6-10 a.m. and 2-7 p.m. on weekdays. For the SH 121 project, TxDOT has decided to open and close the shoulder lanes not only during the peak hours, but also at other times of the day as needed, based on real-time traffic conditions. This would allow TxDOT to reduce congestion in the case of an emergency or during major special events that generate off-peak traffic. Through state-of-the-art ITS equipment, a traffic management center will monitor conditions on the corridor and open the shoulder for use as congestion arises or in anticipation of increased traffic. Dynamic signs will actively inform motorists when the shoulder is open for use.

Stakeholder Communication

Communication has been critical to the project’s smooth progress to date. The project involves many public and private stakeholders, including TxDOT’s Fort Worth and Dallas District, North Central Texas Council of Governments (NCTCOG), FHWA, Bedford and Euless Police Departments along with  various safety and emergency response stakeholder groups, such as local tow-truck agencies.

“We had numerous meetings with various stakeholders about the SH 161 project implementation and the lessons we learned,” said Cordary. “We met with them to explain what we are implementing at SH 121, how it would work, heard their concerns and have thought about how we would solve them.”

The construction of the project began in January 2019 and is expected to be completed in   2020. The project is expected to accommodate the existing and future traffic volumes for the next 10-15 years and improve the safety conditions of the road.

“This project shows how innovation can be used to solve a transportation challenge in a cost-effective manner,” said Cordary. “At TxDOT, we are always looking for different types of strategies to quickly implement solutions. This is another tool in the tool box that transportation departments can use to mitigate congestion.”


Nancy Mitchell, P.E., is a Senior Associate at Lockwood, Andrews & Newnam, Inc. (LAN), a national planning, engineering and program management firm. She can be reached at ndmitchell@lan-inc.com.

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