Real-time radio traffic reports tend to be spotty at best. But a company called AirSage is using a proprietary software algorithm to identify the number, speed and density of cell-phone signals on the road to determine where traffic clogs are forming. It makes sense: stalled phone signal equals stalled car.

AirSage receives a continuous feed of radio-signal data from Sprint. It currently sells its analysis to governments and television and radio stations in 46 American cities. But the company makes no secret of its plans to provide the data to cell phones and GPSs.

Google already provides real-time traffic reports on its Google Maps Mobile service for 30 U.S. metropolitan areas, though it doesn’t work on all phones and you have to download the maps. likewise provides real-time reports–and will even e-mail you about traffic conditions before you begin your commute. Garmin, Magellan and Pharos also offer traffic reports on their GPSs.

What’s the downside to these? Read after the jump.

These services are clearly becoming a crowded party. AirSage may or may not have an edge in accuracy, but how many commuters truly have an alternative route that would save them time? How much advance notice about a tie-up does a driver require to find a more expedient way home? Another problem: all these maps and gizmos in the car provide the kinds of distractions that cause accidents. This is one of the worst ways that traffic tie-ups are created.