Ever travelled in a taxi and marvelled at the cabby’s knowledge of a city’s short cuts? You may soon be able to take advantage of that know-how in your own car. Initial tests of a virtual cab driver suggest that it could shave over 10 per cent off journey times through crowded urban streets.
The taxi-driver technology is Microsoft’s latest foray into the crowded market for route-finding services. Many try to beat jams by tracking traffic conditions, but Microsoft thinks that the hard-won knowledge of local drivers might give it the edge.
The system, known as T-Drive, starts by monitoring the routes taken by cabbies at different times of day. To test their idea, the researchers used three months of movement data, representing 400 million kilometres of travel, from a fleet of 33,000 taxis in Beijing, China. The taxi trajectories were merged to reveal the roads that cab drivers prefer. Given a request to navigate between any two points in the city, the system could then choose a route based on the roads that are popular with cabbies at that time of day.
For a real-world test, the Microsoft engineers asked a pair of drivers to travel between two locations in Beijing: one was given a route suggested by T-Drive, the other used Google Maps. Averaged over 30 trials, the two systems produced routes that were roughly the same in length. But T-Drive seemed to know how to avoid stoppages: it produced average drive times of 23 minutes, almost 4 minutes faster than Google Maps.
Yu Zheng, an engineer at Microsoft Research Asia in Beijing, says the advantage comes from the drivers’ intimate knowledge of Beijing streets. The cabbies know which traffic lights are slow to change and which junctions get snarled up during rush hours. Rival systems, which use information on the speed at which traffic typically travels on different roads, do not incorporate such detailed local knowledge.
Zheng says he is working with Microsoft’s Bing Maps team and that T-Drive could in principle be used in any city for which data on taxi routes is available.
Researchers working on other route-finding projects say that Zheng has taken a novel approach by focusing on taxi routes. But Dieter Pfoser of the Institute for the Management of Information Systems in Athens, Greece, questions Zheng’s decision to compare T-Drive with Google Maps, which he says is not the route-finding market leader. Other rivals include technology developed by TomTom, a company based in Amsterdam, the Netherlands, which bases routes on traffic data harvested from the millions of people that use its navigation devices.
Zheng presented his work last week at the ACM Sigspatial International Conference on Advances in Geographic Information Systems in San Jose, California.