Singapore leads the world in fighting traffic with technology. Vehicle sensors are ubiquitous, and so are message signs warning drivers of upcoming jams. Drivers are even charged higher tolls during rush hour. But when the island government seeks to boost the IQ of these “intelligent highways,” it turns to Der-Horng Lee, a civil engineer at the National University of Singapore. He is in demand among transportation engineers and companies worldwide, helping them write better software that models traffic and controls road signals and signs in real time—for example, changing urban stoplight sequences on the fly as drivers flee rush-hour highways. Lee says traffic prediction is like weather prediction, only tougher. Predictions must be done quickly and account for the fact drivers might change plans after hearing them. The key is having the right algorithm, based on the right traffic simulation model. Most models assume group behavior, but Lee’s “microscopic” models acknowledge that some traffic-bound drivers will sit in the mess while others will cut through city streets or choose a longer highway route.