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Google's autonomous cars know how to deal with cyclists, but are assertive when they need to be Google

A cyclist who was stuck in a two-minute confrontation at a junction with a self-driving Google car says he would still rather share the roads with robots and software than human drivers. Autonomous car experts have also praised Google for giving its cars a sense of caution, but to be assertive when needed.

Gregg Tatum, a keen cyclist who clocks up 6,000 miles each year, encountered one of Google's self-driving Lexus cars at a four-way stop intersection, where the first to reach the junction has the right of way. The Lexus stopped at the junction a second after Tatum, but hesitated when he moved slightly to keep his balance.

"As the car finally inched forward, I was forced to rock the handlebars to hold my position," Tatum posted on the Roadbike Review forum. "Apparently, this motion was detected by one of the sensors and the car stopped abruptly. I held the bike in balance and waited for another several seconds and the cycle repeated itself ... the car inched forward, I shifted my weight and re-positioned the bars and the car stopped. We did this little dance three separate times and the car was not even halfway through the intersection," .

This "dance" continued for "about two full minutes" Tatum said, before the car finally set off, certain than he was not going to cycle across the intersection in front of it. The incident was monitored by two Google employees sitting in the modified Lexus, which is covered in cameras and sensors to help it navigate streets without driver intervention. Tatum said: "The two guys inside were laughing and punching stuff into a laptop, I guess trying to modify some code to 'teach' the car something about how to deal with the situation."

'I felt safer dealing with a robot driver than a human'

Despite the car being uncertain of what to do , Tatum praised its road manners: "It was an interesting experience and I noticed that I actually felt safer dealing with a robotically-operated vehicle than one with a human driver."

Google's autonomous cars monitor the body movement of cyclists to work out what they are about to do. Sensors measure the distance between a cyclist's hand and head to work out whether they are turning or stopping. The car's algorithms also look at the angle at which the cyclist's elbow is bending, plus the size and shape of their hands, arms and head. Doing this, the car can anticipate what the cyclist will do, even if they keep changing their mind.

Speaking to Robotics Trends, autonomous car consultant Brad Templeton, who used to work with Google's self-driving car team, said: "At most four-way stops, if you don't assert your legal right-of-way, others will grab it... so you have to change the 'I will never advance if somebody else is there' caution to add a little assertiveness. If you don't, you will sit too long at a busy stop waiting for a clear slot."

Google says its autonomous cars will be ready to transport passengers by 2020. Apple is rumoured to be producing its own autonomous car and has the same optimistic launch target.