JOLIET, Ill. — In a modest milestone for President Obama’s high-speed rail vision, test runs started zooming along a section of the Amtrak line between Chicago and St. Louis at 111 miles per hour Friday.

The 30-mile-per-hour increase from the route’s current top speed is a morale booster for advocates of US high-speed rail who have watched conservatives in Congress put the brakes on spending for fast train projects they see as 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 bullet trains across Europe and Asia at 150 miles per hour and faster.