North Texas drivers are starting to notice something new blinking overhead on I‑35W north of downtown Fort Worth: digital speed-limit signs that can change on the fly when traffic or weather goes sideways.
TxDOT is rolling out these variable speed-limit signs across the state. The electronic boards let engineers temporarily lower the posted limit – usually by no more than 10 mph – when crashes, construction, heavy congestion, or bad weather make the normal speed unsafe. The limits can be adjusted remotely and paired with mobile message boards in work zones so drivers get both the number and a quick explanation.
According to the Fort Worth Star-Telegram, crews have started mounting the new digital speed signs along I‑35W just north of downtown as part of a broader TxDOT deployment. The paper reports that each board shows the temporary limit for a defined stretch of highway and that engineers can change the display from a central traffic operations center.
What the law allows
House Bill 1885, passed by the Legislature and taking effect in 2023, gave local TxDOT engineers the power to set temporary speed limits without waiting for approval from the statewide transportation commission, according to The Texas Tribune. The law says an altered speed is only in effect when it is actually posted, and in most cases, the reduction cannot be more than 10 mph below the regular posted limit.
Pilot tests and the research
TxDOT did not flip the switch statewide without testing. Variable speed limits were first tried in 2014 at pilot sites in Temple, San Antonio, and Eastland County, with the deployments evaluated by the Texas A&M Transportation Institute. The ITS/TTI evaluation found safety benefits at each location and strong benefit-to-cost ratios, while also flagging the need for permanent overhead sign structures, reliable sensors, and ongoing public outreach.
The 2021 I‑35W pileup that pushed lawmakers
The deadly 133‑vehicle pileup on I‑35W in February 2021, which killed six people, added political urgency to the issue. Federal investigators cited maintenance problems and speeding as contributing factors. Coverage of the federal probe by The Dallas Morning News notes that investigators recommended installing sensors and other countermeasures, including variable speed limits.
How the signs work and where they’ll appear
When TxDOT activates the system, drivers will see the temporary limit on overhead or roadside digital signs, often paired with a second message board that explains why the number changed. Permanent signs can be updated from a control center, and portable trailer-mounted signs may be rolled into short-term work zones to extend the system where needed…