Evaluating Traffic Signals
When TxDOT receives a request for a new traffic signal on the state highway system, the local district office conducts an engineering and traffic study of the proposed location. To justify a new signal, traffic conditions must meet at least one of nine minimum standards, also known as “warrants.” Part 4C of the Texas Manual on Uniform Traffic Control Devices (TMUTCD) specifies these warrants, which are based on guidelines set by TxDOT and the Federal Highway Administration.
Traffic engineers determine if a signal is the proper way to control traffic by carefully evaluating the number of vehicles and pedestrians that use the intersection. They also consider the layout of the intersection, development in the area, delays experienced by motorists during peak hours, average vehicle speeds, future road construction plans and the number and types of traffic crashes recorded.
Examples of information used by traffic engineers to evaluate traffic signal requests include:
A traffic signal evaluation can help assess whether a new signal is the correct answer for a particular location. In some instances, a new traffic signal is not the solution. When a traffic signal is unwarranted because of current conditions, the proposed signal may reduce the number of right-angle crashes but may actually increase the total number of crashes particularly rear-end collisions.
Each TxDOT district office is headed by a district engineer. This individual has the authority to approve a new traffic signal pending satisfactory findings of the district traffic engineer’s study and evaluation.
Cities and counties are usually responsible for traffic signals on city streets and county roads. Local governments share responsibilities with TxDOT regarding state highways when a city’s population exceeds 50,000. This includes the costs to develop, install and operate traffic signals.
When roadways intersect the state highway system, TxDOT handles the installation, operation and maintenance of traffic signals. Our district employees work hard to evaluate all requests for signal lights.
Several factors impact the time it takes to install a traffic signal, such as the need for city or county coordination, preparation of engineering plans, and the complexity of contract awards and installation. If plans proceed smoothly and funds are available, an approved traffic signal could be installed in one to two years.
Traffic signal requests are sometimes denied because the location does not meet at least one of the nine warrants specified in the TMUTCD. In some cases, even if a location satisfies one or more of the required warrants, the request may not be approved, because it could be more of a hazard than an aid. For example, if a traffic signal is requested near a sharp curve with a limited view of the intersection, a signal installation at that location may increase occurrences of vehicle crashes, rather than reduce them.
Other reasons for disapproval may be based on the traffic engineer’s judgment that an alternative traffic control method is more suitable for the location than a new signal. This could include requesting an increased law enforcement presence at the location, improving visibility and public awareness of the intersection, improving pavement markings at the roadway location, or installing flashing warning lights or additional signs.
TxDOT traffic engineers will also consider the possibility that placement of an unnecessary signal could have other undesirable impacts such as excessive and unnecessary delays, public disregard of the signal and traffic detouring to less desirable routes to avoid the signal.
TxDOT is responsible for building and maintaining the state highway system. We have no authority to cite vehicle violations of any kind. That jurisdiction falls under the Texas Department of Public Safety and local law enforcement authorities.
For more information, contact your local district office.