Here's a robot that I built last year to follow the lanes of a small test track. This was built 24 hours before attending Chris Anderson's DIY Robo Cars meetup. I was told about it and thought it would be fun to show up and participate. Unfortunately the rules are a bit bizarre, as it's not about staying in the lines but making it "around the track", which is a very loose rule. Pretty much, you can win this meetup competition if your robocar can drive a circle the fastest, whether in the lines or not.
My intention was to stay in the lines, because that made sense to me. But hey, I might be crazy assuming robocars are meant to actually stay in a lane on a road shrug
The day before the meetup, I didn't have any material to make a real test road, so I placed white pieces of paper on the floor. Had to keep the windows closed because they weren't taped down, and the wind moved them - haha. The test robot I used was simply a modified AdventureBot. Using ARC, I created multi-color profiles for the lanes and off my robocar went...
I attended the meetup the following morning. Like i mentioned earlier, a little disapointed in the lack of real-world vehicle rules... but it was still fun! My little robocar, that took less than an hour to build an program with ARC was the only robot to make it around the track continuously... that is, until someone elses road-raged robot drove into mine
The next day, I was still a little caught up on perfecting the ARC features for this exercise. I wanted the robot to move a little quicker, which was limited by the WiFi camera frame rate, however. I did end up making a better track in my house, and like a model train, I let my new robocar drive the mini-road until the batteries died!