Design concepts are a dime a dozen, but every once in a while you see one that seems too good not to be real. One example: The Light Lane, which allows any bike rider to project a traffic lane around them.
If you've never ridden a bike in a city, the idea's brilliance takes some explaining. Though many cities, including New York, have right-of-way laws for bike riders, drivers ignore them, treating bike riders like traffic cones. (That's one reason why urban bike riding remains so dangerous.) Bike lanes dramatically improve the situation, but they cost up to $50,000 a mile to install.
The light lane finally allows bike riders themselves to right the situation, using a cheap lasers to project a lane around the rider. Of course, it only works at night, but the idea goes a long way towards fixing a major obstacle in making bike riding more mainstream in cities, and it doesn't require any fancy tech.