Microsoft is applying the power of the microprocessor to a traditionally low-tech problem: traffic jams. The firm is launching a web service that will give driving directions specifically designed to avoid busy spots. It's based on a technology called 'Clearflow', which took researchers five years to develop.

The idea is that every time traffic backs up, it causes an effect that spreads across adjoining roads. Clearflow can quickly measure and analyse the way live traffic problems affect side streets as well as major highways.

The system will cover 72 cities and will be free to use as part of the map function at Live.com. That site already had a directions feature, but it didn't always work well because it only took account of major roads.

Microsoft has warned that the new system might sometimes seem counterintuitive. For example, when a major road is busy, drivers may be told to stay on it because side streets are actually more congested thanks to people trying to avoid the original hold-up.

The system is based on research in Seattle where Microsoft employees carried GPS systems in their cars over four years, providing details for 16,500 trips totalling 125,000 miles. Once they'd analysed the data and produced a model for Seattle, they applied the technology to other cities and the system now covers individual details for around 60 million different sections of road.

As well as assessing live traffic updates, the system takes into account the likely effects of rush hour, poor weather or major events at local arenas and stadia. (Source: nytimes.com)

Microsoft technology is already used by Inrix, the firm which runs traffic alert systems for the entire interstate and highway system. However, they've chosen not to use the Clearflow system, instead relying on GPS trackers in vehicles, mobile phones and road sensors. (Source: nwsource.com)

The traditional system used by Inrix, which displays actual current conditions, is much more suited to lengthy roads such as expressways where jams don't have as many knock-on effects. But Microsoft's Clearflow seems to make much more sense in cities where it's important to predict how a traffic jam on one street will affect other roads in the vicinity.