An early-warning system for your bike

In the summer months, I really enjoy riding a bike along some of the flatter roads and trails around my small Vermont town. But sharing some of those roads with cars can be a dicey proposition. There???s one dirt road in particular, where no matter how often I scan my mirror or sneak a look over my shoulder, it seems that sooner or later I get surprised by a car zipping by. I???ve often imagined fitting an ultrasonic sensor to the bike to warn me of incoming traffic, but most of those have a range of less than 10 meters, which is worse than even my mediocre human senses. A lidar???similar to a radar system, but with laser pulses instead of radio waves???would have the longer range I need, but lidars have traditionally been too expensive for my biking needs. ??? This changed last year when startup PulsedLight, of Bend, Ore., announced Lidar-lite, a crowdfunded lidar detector less than half the size of a deck of cards, with a range of up to 40 meters and an accuracy of plus or minus 2.5 centimeters, all for US $89.