National Geographic : 1983 Jul
Serpentine symbol of the auto's preeminence,the four-level interchange of the Santa MonicaFreeway (left, top level) and the crossingHarborFreeway in Los Angeles handles more than 400,000 vehicles a day. With budget limitations curtailingexpansion of California's 15-billion-dollarfreeway system, state transportationofficials seek to smooth trafficflow with on-ramp signals,signs that flash warnings of disruptionsahead, and in-pavement sensors that give highway patrolmen early notice of stoppages due to accidents. Downtown Detroitappearsthrough the windshield and on the dashboard (above) of a 1982 Buick equipped with a prototype GeneralMotors navigation system. Using radioguidance signals, the system's computer indicates the driver's location on street grids projected by reprogrammablecartridges. GM plans to link the device to satellites and offer it as an option on top-line models within the decade.