Travel time information is of interest to both road users and road network operators. The direct travel time estimation method such as probe vehicles has high accuracy but it requires a high probe rate to collect the complete travel time information of a road network, which is too costly for the daily operation of a road network. The indirect method by point sensors assumes stable speed within a roadway segment and it has low accuracy when the traffic becomes congested. The project explores a fundamental advancement in the theoretical and practical research related to travel time estimation in a freeway network by matching vehicles in a network of traffic surveillance cameras. The accurately computed travel time will sustain the transportation system in a manner that is more effective, more efficient, and more economic competitive.