Jan 10 (Reuters) - RR.AI, a unit of self-driving technology startup Robotic Research, and U.S. bus maker GILLIG said on Monday they will jointly develop driver assistance systems and self-driving technology for commuter buses in the United States.

Making taxis autonomous has proved more difficult and expensive to develop than expected, but investors have pumped money into trucks and other commercial vehicles where automation could be viable sooner.

RR.AI and GILLIG said they would jointly develop Level 4 autonomous vehicle technology for buses, which would allow a vehicle to drive itself under certain circumstances, such as in a depot, but most of the time a human driver would be needed.

They said the technology could protect drivers through safety features, including automatic emergency braking, precision docking, blind spot detection and pedestrian avoidance.

"We believe the partnership with GILLIG will improve the safety and wellbeing of drivers, pedestrians, and roadway users all while increasing efficiency for transit authorities and lowering costs," RR.AI Chief Executive Alberto Lacaze said in a statement.

GILLIG said it expects to implement these technologies across all its bus models, but will deploy them first in its latest electric bus model.

The U.S. bus market is dominated by GILLIG, Canadian NFI Group Inc's New Flyer unit, and Canada-based Novabus, a unit of Volvo AB.

Robotic Research said last month it has raised $228 million from investors including SoftBank to scale up RR.AI's solutions for trucks, buses and logistics vehicles.

GILLIG's owner Henry Crown & Company participated in that funding round. (Reporting By Nick Carey; editing by Barbara Lewis)