City buses have started testing out new tech that can help stop crashes, officials said Thursday.

Four buses in Manhattan, Brooklyn and Queens now have external speakers that give a warning when a bus turns, alerting pedestrians and cyclists.

Another new system uses sensors that warn bus drivers with lights and audio alerts if the bus is about to hit someone crossing the street. It can detect pedestrians on both sides of the bus, as well as the front.

The collision avoidance system has been installed on two buses that come out of the Flatbush Depot.

"Unfortunately, the world has gotten more automated. There are more distractions," said Steve Vindal, the bus department's vice-president for safety and training. "People are walking with their phone, typing a text message, checking their e-mail."

If the devices get positive feedback from drivers they will be expanded to 200 buses.

Citywide installation would cost $20 million for the pedestrian warning system and $57 million for the collision avoidance system.

"This is something we've been asking for many years, and will help drivers with blind spots," said J.P. Patafio, a vice-president at TWU Local 100.

M9 driver Salvatore Perrotta, 51, tried out the technology on Thursday morning. "It will help you drive safer and be more vigilant in how you drive," he said. "It will pre-warn you -- people cross on the side of you. We have to watch everythng".