Fortune Magazine in America is reporting that Google is preparing to expand its self-driving car project to four more US cities.It's quoting "a recent Federal Communications Commission document" which says that Chris Urmson, director of the Google self-driving car program, has asked the FCC to renew an "experimental authority licence" that allows it to test radio transmitters in the 76 GHz range'likely used by the radar system on its cars.The request asks for a 24-month extension of the license in Google's home in Mountain View, California and in Austin, Texas where the self-driving cars are currently being tested as well as four additional cities. The names of the cities were redacted from the request.Google has an ambitious plan to introduce self driving cars by 2020.  Fortune says Google has to test in other cities, particularly those with different weather conditions, if it hopes to deploy these cars for widespread public use.