While people had varying opinions on autonomous vehicle technology in a recent survey by the University of Michigan Transportation Research Institute, most did not want to give up complete control of driving to the automobile.

UMTRI researchers Brandon Schoettle and Michael Sivak polled 505 licensed drivers to determine how they felt about different levels of vehicle automation. These included completely self-driving vehicles, which control all safety-critical functions and can even drive without a passenger; partially self-driving vehicles, which control safety-critical functions and require only occasional control from the driver; and vehicles without self-driving capability, which assist the driver with various advanced technologies but delegate all safety-critical functions to the motorist.

The largest share of respondents, 43.8 percent, said they would prefer to retain full control while driving a vehicle. A total of 40.6 percent said they preferred a partially self-driving vehicle. Only 15.6 percent said they would like a completely self-driving vehicle.

"Self-driving vehicles are often discussed in regard to their potential safety, energy-consumption and environmental benefits, or the existing technical challenges that must be overcome for their successful implementation," said Schoettle. "However, less attention has been paid to considering the actual level of automation, if any, that drivers desire in their vehicle."

Male drivers under the age of 45 were most likely to favor a partially or completely self-driving vehicle. Partially self-driving vehicles were the most popular among men, with 41.2 percent favoring this option.

Women were more likely to want a vehicle with no self-driving capability. A total of 47.6 percent said they would prefer that their vehicle not be autonomous.

Older drivers were also more wary of autonomous vehicles, with half of all respondents ages 60 and older saying they did not want their vehicle to be self-driving. Only 11 percent of this age group favored a fully autonomous vehicle.

However, drivers between the ages of 18 and 29 were only slightly more likely to support the idea of riding in a fully autonomous vehicle. While 17.1 percent said they would like a self-driving vehicle, 37.5 percent wanted to retain control over driving.

About two out of every three respondents said they would be at least moderately concerned about riding in a completely self-driving vehicle, but less than half said they would be concerned about riding in a partially autonomous vehicle. Women and older drivers were more likely to be concerned about riding in an autonomous vehicle.

Drivers also favored keeping the familiar features of a steering wheel, accelerator, and brake pedal in a completely self-driving vehicle. Nearly all respondents—96.2 percent—said they would want those features in the vehicle even if driving was left to the vehicle itself.

For partially self-driving vehicles, 59 percent said they would like to see a combination of sound, visual, and vibration warnings to let a driver know when they have to take control of a vehicle. About 19 percent said audible and visible warnings would be sufficient.

The report comes shortly after Google reported the first injury accident involving one of the 23 self-driving vehicles the company is testing. Three occupants were injured when one of the company's autonomous cars was rear-ended at a traffic signal near the company's California headquarters.

These vehicles have been involved in 14 collisions since Google began testing the self-driving prototypes, including 11 incidents in which the vehicle was rear-ended. The company says it has not been at fault in any of the collisions and blames human error and distracted driving among other drivers for the incidents.

Proponents of autonomous vehicles say they are not affected by several factors that lead to crashes, including intoxication, distraction, or aggressive driving. Richard Read, writing for the automotive site The Car Connection, suggests that people tend to overestimate their own driving abilities and be nervous about turning control over to an autonomous system. He says automakers that develop autonomous vehicles will have to work to address these feelings in order to successfully market vehicles to the public.