Study Suggests Using Two License Plates Saves Resources for States, Law Enforcement Agencies

front bumper of truck showing empty license plate holderA recent study by the Texas A&M Transportation Institute (TTI) suggests that states that require vehicles to have two license plates save valuable time and resources in the areas of enforcement, tolling, parking and homeland security. The study also found that the use of two license plates for vehicle identification purposes increases the efficiency and accuracy when evaluated by an individual or using automatic license plate reader (ALPR) technology.

“As a cost-cutting measure, a lot of our enforcement — be it tolling, parking, homeland security or law enforcement — has become an automated process,” said Melissa Walden, Center for Transportation Safety Senior Research Scientist and Project Manager. “The license plate is a key factor in vehicle identification for that automation, and without proper identification, states are losing a large amount of revenue.”

In the United States, 31 states require two plates (front and rear), while the remaining 19 states only require one rear plate. Researchers examined multiple states — two states that require one license plate (Pennsylvania and Arizona) and two states that require two license plates (Maryland and Texas) — through interviews with enforcement and tolling agencies as well as vehicle observation. Additionally, ALPR data were examined in both types of states.

“The interesting thing about this project is that it has allowed us to see how something as seemingly small as a license plate can have a tremendous impact on enforcement and operations,” said Walden.

With the integration of more ALPR technology into enforcement, two plates increase the opportunities to identify vehicles (speed detection, stolen vehicles, red‐light running, etc.).

The study found:

  • Front plates were easier to read in the daytime environment because of the effects of sun glare.
  • The lack of front plates has a significant impact on photographic evidence related to fining toll violators. In Virginia, 23 percent of toll violations could not be pursued because the rear plates were unreadable.
  • Without front license plates, the E‐470 corridor in Colorado would lose at least 34.5 percent ($23.1 million) of their toll revenue annually.
  • U.S. Customs and Border Protection (CBP) reports that the number of plates not read on vehicles, because of the lack of two plates, made a significant impact in their border processing; 6 percent of plates at the northern border and 3.4 percent of plates at the southern border were unreadable. With the volume of vehicles processed every day, along with homeland security concerns, the front plate allows CBP to operate more effectively.
  • Law enforcement in Pennsylvania, a one-plate state, would like to see two plates to improve their ability to read plates (especially large commercial trucks) using ALPR technology. Sixteen percent of the plates that pass through the tolling facilities are unreadable, which impacts the state’s ability to pursue toll violators.
  • Phoenix’s Sky Harbor Airport reports that 10,000 parking transactions per year (an average of $30 per transaction) rely on ALPR plate reads to determine accurate charging. Fifteen percent of those transactions had to be processed manually because of sun glare on the rear plates.
  • Field studies showed a 97 percent read rate for parked vehicles in two-plate states and 76 percent in one-plate states. For moving vehicles, the read rate in Maryland and Texas was 89 percent, in Pennsylvania and Arizona it was 22 percent and 58 percent, respectively, on the roadways connecting Maryland and Pennsylvania. These read rates are based on the opportunity to read a front plate.
  • For states with more than 100 miles of toll roads, one-plate states account for 55 percent of the total tollway miles. As fiscal pressures mount, efficiency in the collection of tolls and the pursuit of violators become critical. Front plates increase the likelihood of collecting that revenue.