The National Transportation Safety Board issued a report on its investigation of a brutal multi-vehicle accident that took place during the February 2021 ice storm, faulting the company responsible for the freeway's operation and maintenance.

According to a release, the NTSB found that North Tarrant Express Mobility Partners Segment 3 (NEMP S3) failed to monitor and address icy roadway conditions, contributing to the devastating crash.

The accident occurred on February 11, 2021, in the southbound toll lanes of I-35W, in which six people died, at least 65 were injured, and 36 were taken to area hospitals.

The crash began at 6:04 am, when a car near the Northside Drive exit struck the concrete barrier on the right side of the toll lanes. Other vehicles in the southbound toll lanes then began to slide, spin, and strike the barriers.

At 6:13 am, a large truck crashed into some of the disabled vehicles that were blocking the travel lanes. Other vehicles were unable to stop, leading to a multivehicle crash blocking all southbound toll lanes.

In the days before the crash, the area had experienced 36 consecutive hours of below-freezing temperatures.

North Tarrant Express Mobility Partners Segment 3 was the company responsible for operations and maintenance on the I-35W right of way.

According to the NTSB, they pretreated the two southbound lanes with a liquid brine solution 44 hours before the crash. The area had experienced 36 consecutive hours of below-freeing temperatures.

On February 11, employees spot-treated some sections with salt, but did not treat the elevated portion of I-35W where the crash occurred.

Maintenance crews drove north on I-35W about 45 minutes before the crash and visually checked the road, but they detected no moisture and applied no salt.

NTSB investigators found that NTEMP S3’s roadway monitoring process was deficient because, as precipitation and freezing temperatures continued and conditions deteriorated on the morning of February 11, company personnel did not identify the elevated portion of I-35W as needing additional de-icing treatment, which left the roadway surface icy.

However, North Tarrant Express Mobility Partners Segment 3 say they disagree with the assessment.

"Video footage from the morning of February 11 confirmed that precipitation began mere minutes before the accident unfolded," the company said. "Hours earlier, we had posted dynamic signage within the vicinity of the accident site, warning drivers of icy conditions and to drive with caution. We also had deployed permanent signage warning drivers that bridges could ice in cold weather."

NTSB also found that drivers were driving too fast for winter weather conditions, contributing to the severity of the crash. The roadway has a 75-mph speed limit.

The NTSB is recommending that Texas do the following:

• install of variable speed-limit signs
• add sensors to reduce response times to weather-related hazardous road conditions
• provide training to Texas toll road facilities on how to better respond to winter storms

The NTSB also reiterated previous recommendations in favor of automated speed enforcement and increased connected vehicle technology deployment.