Manhattan District Attorney Cy Vance sent a letter to state lawmakers warning that a bill to prevent police from detaining bus and taxi drivers at crash scenes would undermine law enforcement’s ability to collect evidence of impaired driving.

The bill, which sailed through the State Senate yesterday with no public notice and without a public hearing, would bar police from detaining many professional drivers — including bus drivers, taxi drivers, and limo drivers — following a crash. Instead, a driver suspected of breaking the law would receive a desk appearance ticket.

The bill passed the Senate at the behest of the Transport Workers Union, which doesn’t think bus drivers who kill and injure people should be subject to charges under the NYC Right of Way Law.

On Tuesday, Vance sent a letter to Senate Majority Leader John Flanagan and Assembly Speaker Carl Heastie. It read:

Although the amended bill attempts to exclude drivers who may be driving under the influence of alcohol, police officers often conduct field sobriety tests even when there is no immediate suspicion of impairment, and must often wait a significant period of time for the arrival of equipment to conduct those tests. By prohibiting the detention of omnibus drivers at the scene of collisions, the bill prevents law enforcement from gathering evidence vital to bringing criminal charges in appropriate cases.

“In a city full of pedestrians and cyclists, we should be working on ways to make the city safer for New Yorkers, and certainly not promoting changes that would hold some drivers to a lower standard than others,” Vance wrote. “For these reasons, I urge our lawmakers to vote against this bill.”

NYPD and Mayor de Blasio’s office oppose the bill, along with Families for Safe Streets, Transportation Alternatives, and Mothers Against Drunk Driving.

The bill is now in the Assembly, where it’s the last day of the 2015 legislative session. Families of people killed by New York City drivers are in Albany today trying to convince Assembly members to stop the bill. You can support them by contacting your representative right now.