CHICAGO — In a modest milestone for President Barack Obama's high-speed rail vision, test runs will start zooming along a small section of the Amtrak line between Chicago and St. Louis at 110 mph on Friday.

The 30-mph increase from the route's current top speed is a morale booster for advocates of high-speed rail in America who have watched conservatives in Congress put the brakes on spending for fast train projects they view as expensive boondoggles. But some rail experts question whether the route will become profitable, pose serious competition to air and automobile travel, or ever reach speeds comparable to the bullet trains blasting across Europe and Asia at 150 mph and faster.

U.S. Transportation Secretary Ray LaHood and Illinois Gov. Pat Quinn are scheduled to be on board when an Amtrak train hits 110 mph for the first time in Illinois. But it will only maintain that speed for a short time, somewhere along the 15 miles between Dwight and Pontiac, before braking back to more normal speeds.