A study quantified the potential benefit of a pretrip advanced traveler information system (ATIS) to travelers in the Washington, D.C., region for the commuter objective of consistently on-time arrival. Paired driver commutes were simulated with a 15-month archive of regional travel times from SmarTraveler.com, an Internet provider of real-time data on travel time. One driver used a personalized pretrip notification service in selecting departure time and route, while the paired counterpart maintained a habitual trip departure time and route. The pairs' trip arrivals were compared to quantify the effects on time management of a prospective notification service prescribing departure time and route. Approximately 25.9 million paired driver trials were modeled across a network of 55 nodes and 150 links, traversing 711.8 mi of roads in the Washington, D.C., metropolitan region. Trips were simulated for arrivals at 15-min intervals between 6:30 a.m. and 6:30 p.m. on workdays from each node to every other node. Overall, regular use of the pretrip ATIS is shown to benefit commuters whose objective is arriving on time. At low levels of ATIS market penetration, routine ATIS use could reduce early arrivals by 56% and late arrivals by 52%. Benefit in vehicle travel time is minimal. By applying a utility function to each trip, it was calculated that ATIS service reduces aggregate travel disutility by 15%. Approximately 67% of trips (origin-destination) derive a net benefit from routine ATIS use, while 40% benefit by more than $60/year. Benefits are fairly distributed across the year and are generally greatest during the evening peak.