Humble and Houston police say a man was pushing an SUV early Monday morning along the feeder road of Highway 59 when another driver slammed into him.
It happened around 11:15 p.m. Sunday on the bridge over the San Jacinto River.
Officers say the driver sped off without helping the man, who was lying in the middle of the road with a severed leg.
Police say a witness followed that driver and relayed his license plate and vehicle description to police. Another passerby stopped and made a makeshift tourniquet for the injured man, who was taken to a nearby hospital.
The northbound feeder road was closed for hours while authorities conducted their investigation.