WASHINGTON — President Joe Biden’s nominee to serve as the top auto safety regulator vowed to address the massive increase in U.S. road deaths, according to his prepared congressional testimony.

Steven Cliff, who was tapped to head the National Highway Traffic Safety Administration, told a Senate panel Thursday the U.S. has “seen an unprecedented rise in roadway fatalities. I am committed to turning this around.”

He added the U.S. must learn “how to change a culture that accepts the loss of tens of thousands of people in roadway crashes as inevitable.”

U.S. traffic deaths soared by 18.4 percent in the first six months of 2021 compared with the same period a year earlier, representing the most deadly first half of a year on American roads since 2006, NHTSA said. It was the largest six-month increase recorded since the current tracing system has been in use since 1975.

Cliff, a former California Air Resources Board official who since February has served as NHTSA’s deputy administrator.

Cliff said a new infrastructure bill increases NHTSA’s budget by 50 percent and “will improve our understanding of where and how crashes happen by improving data quality and expanding electronic reporting to move from paper-based data collection systems to digital systems.”

Cliff has been a key figure in the Biden administration’s proposed rewrite of vehicle fuel economy standards through 2026 and is overseeing its safety investigation of EV maker Tesla Inc.

During his testimony, he said he hopes the agency can complete its investigations into Tesla soon.

Cliff was asked about the agency’s probes into Tesla and he said “we hope to have those investigations wrapped up soon.” He said he did not have a “precise timeline.”

The agency, part of the U.S. Transportation Department, faces a backlog of pending auto safety regulations and has not had a Senate-confirmed administrator since January 2017, the month when Republican former President Donald Trump took office.

NHTSA and the EPA in August proposed reversing the Trump administration’s rollback of Corporate Average Fuel Economy rules. Amid the COVID-19 pandemic, the U.S. has experienced a sustained increase in traffic deaths that NHTSA attributes to impaired driving, speeding, a failure to wear seatbelts and other unsafe behavior.

The Biden administration could unveil final fuel economy and vehicle greenhouse gas emissions rules as soon as next year, officials told Reuters.

“I am committed to making the transportation fleet as efficient as possible, to save consumers billions of dollars at the pump, to improve the nation’s energy security and to protect the environment,” Cliff’s testimony says.