Rail to Denver's Airport.... WHY?

By far the least expensive solution to congestion to and from the airport would be to add capacity to our freeways. And it's also the least expensive. Why are we spending 20% more to get 1/2 the delay savings from rail?

Cost Delay Saved
New freeway lanes $305 61,200
HOV lanes/BRT 337 41,900
Diesel rail 374 29,700
Electric rail 571 30,300

Capital costs in millions, delay saved is annual hours of congestion delay saved by the project. Source: pp. 37-39 of the East Corridor Major Investment Study Final Report.