Illegal Speed Limits on Future North Texas Tollways

September 15, 2005

Allan Rutter, Executive Director
North Texas Tollway Authority
5900 West Plano Parkway, Ste 100
Plano, Texas 75093

Mr. Rutter,

I read with interest a Sept. 15, 2005 Dallas Morning News article by Tony Hartzel titled “Area toll roads to get pricier.” Part of that article detailed NTTA board discussions about speed limits. I am writing to alert you that the board may be considering illegal speed limits.

Here are key quotes from the article:

One option calls for the new toll roads to have the same rates as other roads. Under another scenario, the higher-cost toll roads could have higher tolls. Those tolls also could be based upon lower speed limits or cost, such as community requests for extra amenities. Consultants say that lower speed limits reduce the number of toll road users, thereby reducing revenue potential.

Board members expressed a desire to find a compromise, with most toll roads having the same rate but leaving the option open for higher tolls on certain projects. That most likely would apply to Southwest Parkway and the proposed Trinity Parkway in downtown Dallas, where city leaders have asked for lower speed limits.

(Emphasis added.)

It appears that the NTTA board is considering choosing arbitrary speed limits to satisfy a financial goal. Texas law does not permit the NTTA to choose speed limits in this fashion.

Per section 545.354 of the Texas Transportation Code, Texas Statutes, titled “Authority Of Regional Tollway Authorities To Alter Speed Limits On Turnpike Projects”:

The authority, in conducting the engineering and traffic investigation specified by Subsection (a), shall follow the procedure for establishing speed zones adopted by the Texas Department of Transportation.

This procedure is defined in the Texas Administrative Code Title 43 (Transportation), Part 1 (Texas Department of Transportation), Chapter 25 (Traffic Operations), Subchapter B (Procedures for Establishing Speed Zones). Specifically, rule §25.23 of this procedure requires the speed limit to be set at the 5 MPH increment closest to the 85th percentile speed of passenger vehicles, and variances are only allowed for unusual circumstances such as an above average crash rate, pedestrian traffic, or a lack of shoulders. It is unlawful for the NTTA to establish a speed limit lower than the 85th percentile speed for any other reason, including but not limited to a financial goal, the “design speed” of the roadway, or a desire to placate the whim of a city council.

Simply put, Texas law requires that the posted speed limit be a reflection of the maximum speed used by reasonable drivers.

This policy is further backed up by section 2B.11 of the Texas Manual on Uniform Traffic Control Devices. “Substantial compliance” to this manual is a condition for Texas to receive federal highway dollars. This manual is strict in its requirement for the use of the 85th percentile speed, and it clearly requires that no other considerations are to be allowed besides physical characteristics of the roadway or crash records.

As a side point, no new miles of roadway established after 2002 are eligible for Environmental Speed Limits. Per section 545.353, Transportation Code (Authority Of Texas Transportation Commission To Alter Speed Limits), “the commission may not determine or declare, or agree to determine or declare, a prima facie speed limit for environmental purposes on a part of the highway system.” Since the NTTA is bound by statute to use the same speed zoning rules as the Texas Department of Transportation, the NTTA may not enact environmental speed limits on any roadway that did not already have an environmental speed limit before Sept. 1, 2003. (This is due to the effective date of the bill adding this clause to section 545.353. Please see the NCTCOG’s environmental speed limit web site at for further clarification.) This means that the 5 MPH environmental speed limit reduction currently in effect on the George Bush Turnpike between I-35E and Garland may not be used on the new section of the turnpike between I-35E and I-635. Furthermore, this 5 MPH speed limit reduction may not be part of the speed zoning process on the Dallas North Tollway north of TX 121 or south of Frankford Rd. The 5 MPH speed reduction only applies to roadway segments which had the 5 MPH speed limit reduction before Sept. 1, 2003.

While I enjoy the North Texas Tollway Authority roads, I have observed that currently posted speed limits are almost certainly posted 5-10 MPH below the maximum safe speed that would be determined with a proper speed study. I am alarmed to read the apparent recommendation of even lower speed limits. I hope the Authority refrains from using illegal, arbitrarily low speed limits on future roadways, and I hope the NTTA will consider rechecking speed limits on existing roadways. Every arbitrarily low speed limit on NTTA roads only encourages a dangerous mindset that traffic regulations don’t matter.

Please do not hesitate to contact me if you need clarification of this letter.


Aren Cambre

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