This article is based on a study that analyzed the impacts of employer-based transportation demand management (TDM) strategies and the performance of a transportation system. The study simulated the effects of the Washington State Commute Trip Reduction (CTR) programs implemented by 189 employers on an 8.6-mile segment of I-5 in the Seattle downtown area. This comprehensive dataset included before/after employer trip reduction plans and the origins/destinations of nearly 63,000 commuters working for those 189 employers. The current performance of the selected network was compared to that of a scenario with reduced vehicle trips due to CTR programs added back onto the network. The hypothesis of the research was that a widescale adoption of employer-based strategies is likely to have a measurable difference on the performance of a transportation system. The analysis found the reduction in AM peak delay due to TDM programs implemented in the study area was 152,489 vehicle-minutes and 17,297 vehicle-miles of travel. Savings in PMpeak delay were 169,486 vehicle-minutes and 14,510 vehicle-miles were reduced. Fuel saved in the AM and PM peaks were 3,489 and 4,314 gallons, respectively. Some segments and periods saw significant improvement. The study proved that comprehensive TDM programs could have a significant impact on the operation of a major Interstate corridor.