Looking for open parking spaces in the city is one of the more teeth-grinding rituals for drivers, but researchers at Rutgers University in New Jersey may have hit upon a relatively low-cost solution. They combined ultrasonic sensors with GPS to create digital maps of available parking spaces for Web-based navigation systems, according to Technology Review.

As much as 45 percent of traffic in Manhattan comes from cars wearily circling the blocks and looking for parking spaces, according to a New York City transportation advocacy group called Transportation Alternatives. That problem has driven cities such as San Francisco to create "smart parking infrastructure" that detects vehicles in parking spots using fixed sensors -- a solution that costs $500 for installing and maintaining each sensor. Read more »