I’m late in relaying this, but B. Moore submitted a link to the Houston Real-Time Traffic Map, and described it thusly:

This is an amazing real time traffic map that is quite sophisticated and useful (at least if you live or drive in Houston). It provides real time traffic conditions, color coded by speed, on Houston’s main freeways and is a must when heading out for the daily commute or trip to the airport. Complete with multiple freeway cams, reports of traffic accidents, construction updates, and travel times. It uses the automatic tollway electronic devices installed in some cars (that let you whiz through toll booths and have the charge automatically billed to you), and sensors in the roadway to time how long it takes an individual car to travel a set distance along the different roadways. Then the system does the math and computes speed. It updates once a minute and is very accurate. You can even get it on some mobile PDAs and maybe cellphones.