The NTTA Board of Directors voted to set a 70 mph speed limit on the 121 Tollway.

Official 70 mph speed limit set on
121 Tollway

The NTTA Board of Directors voted during its Jan. 30 meeting to set a 70 mph speed limit on the 121 Tollway.

The Board acted after receiving the results of a speed limit study on Segment 2 of the 121 Tollway, which opened to traffic Aug. 31 and stretches from Old Denton Road in Denton County to Hillcrest Road in Collin County.

Drivers are already accustomed to the 70 mph speed limit on the main lanes of the 121 Tollway as it’s the same as the state-mandated default speed limit, known as the “prima facie limit,” which already was in effect.

The NTTA assumed responsibility of the 121 Tollway corridor from the Texas Department of Transportation (TxDOT) on Sept. 1, per a project agreement. The agreement called for TxDOT to conduct a speed limit study on the toll road’s main lanes after Segment 2 opened.

An NTTA consultant conducted the study using TxDOT procedures, which involved tracking and documenting the speeds of 125 random vehicles. Measurements were taken every one-half mile during weekday off-peak hours during good weather to assess free-flowing traffic.

The information on traffic speeds was then calculated to determine the 85th percentile speed – which is the speed that 85 percent of vehicles travel at or below. The 85th percentile speed is considered the most characteristic representation of safe and reasonable traffic speeds.

Segment 1 of the 121 Tollway – from Denton Tap Road in Dallas and Denton counties to Old Denton Road in Denton County – was built by TxDOT and opened to traffic in summer 2006. TxDOT conducted its initial speed study on that stretch of the toll road in March 2007 and set the speed limit as 70 mph.

The Board’s action means that the speed limit on the entire 121 Tollway corridor that is open to traffic is set at 70 mph.