Work is already underway downstate on the first 90 miles of rail corridor between Chicago and St. Louis.
The project calls for boosting Amtrak speeds to 110 miles per hour.
Critics said the project is too costly and doesn't provide enough benefits.
The study done by the Illinois Public Interest Research Group (PIRG) says that in addition to creating jobs, the high-speed rail line will cut carbon dioxide emissions and reduce highway and airport congestion.