text: Driverless cars are a good idea to a certain point. These cars would not be a good idea because many things would have to be adjusted to existing roads, which would be very costy . In paragraph 3 the author says," These smart-road systems worked surprisingly well, but they required massive upgrades to existing roads, something that was simply too expensive to be practical." This proves that cars like this would require many adjustments, that are not cheap, to existing roads and that the cars.