Wisconsin's four-year HOT lanes pilot project, launched in May 2008, cost US$18.8 million to construct. Halfway into the project, which uses variably priced, or dynamic, tolling to improve highway efficiency, the benefits are mounting. The problem was obvious, and frustrating, to anyone who ever sat in bumper-to-bumper traffic on State Route 167 and watched a lone car whiz by every 20 seconds or so in the carpool lane. But for planners at the Washington State Department of Transportation, the conundrum was
