Why get rid of transponder-read status lights at tolls?

Question

When driving through a toll both with a transponder, it is common to have some form of display feedback to the driver. For example, the US state of Maryland has an explanation here showing the three key components of the system (from a user perspective), including #3, the Driver Feedback Display.

Apparently, the US state of Pennsylvania used to have such indicators, but removed them in 2017, and now drivers going through an equipped tollbooth have no way of knowing whether or not the read was successful without going online to check their account a sufficient number of days later to allow time for the read to post, or phoning the turnpike authority.

This seems like a pretty bad UX decision. Yet it was intentionally made, reportedly "due to a change in federal guidelines." The change in guidelines also seems to have been intentionally made for some reason or set of reasons. What are those reasons? Why is this change considered a good thing to expend time/money/effort on?

---

Hypothesis: This change could impact speeds at tollbooths. For example, if a tollbooth is signed 5mph, and a driver is approaching it at 10 but sees the light acknowledging their tag was read, the driver may just continue through without slowing down further. In the new condition without the lights, drivers may be more likely to slow down more and go through at a crawl to try to increase the probability of a successful read (assuming higher fines for read failures, as is often the case). Any studies about that are welcome in answers.

This would seem likely to increase congestion around tolls and increase environmental costs of tolls, but speed enforcement at 5mph tolls may be a public policy goal, to promote strict rule-following in general. (Is that the reason?)

Answer 1

These changes were made by the DOT to facilitate traffic flow and improve vehicle safety in and around toll plazas.

Background

Green, amber, and red lights are part of standardized system to communicate right of way to drivers via traffic control signals, i.e., stoplights or traffic lights.

Toll plazas like those mentioned in Pennsylvania have been repurposing these same lights to provide toll payment feedback, using green to indicate success, amber to indicate low balance, and red to indicate failure.

The original choice to repurpose traffic lights in these installations introduces the risk of drivers interpreting them as traffic control signals. For example, a driver with a low prepaid EZ-Pass balance could interpret the amber light as an instruction to slow down or yield, resulting in an unintended disruption of traffic flow.

The change only impacts toll plazas that rely on indicators which closely resemble traffic control lights, i.e., stoplights. For example:

Recommended Feedback System

The DOT recommended payment feedback mechanism is the Driver Feedback Display seen below:

Details on New Regulations

Guidance on these systems is provided by the DOT via the Manual on Uniform Traffic Control Devices for Streets and Highways. Within this document, Section 4K.01 Traffic Signals at Toll Plazas states that:

Standard: Traffic control signals or devices that closely resemble traffic control signals that use red or green circular indications shall not be used at toll plazas to indicate the open or closed status of the toll plaza lanes.

Guidance: Traffic control signals or devices that closely resemble traffic control signals that use red or green circular indications should not be used for new or reconstructed installations at toll plazas to indicate the success or failure of electronic toll payments or to alternately direct drivers making cash toll payments to stop and then proceed.

Related Research

In 2006, DOT commissioned a consulting agency to prepare State of the Practice and Traffic Control Strategies at Toll Plazas: Best Practices.

The full history of the change is in National Standards for Traffic Control Devices; the Manual on Uniform Traffic Control Devices for Streets and Highways; Revision; Final Rule.