CHICAGO (CBS/WBBM) – The newest rapid transit cars on the CTA are heading back to the transit agency’s most heavily-used route.

As WBBM Newsradio 780′s Bob Roberts reports, the 10 new cars have already run on all the Chicago Transit Authority ‘L’ lines.

LISTEN: Newsradio 780′s Bob Roberts reports

A return to the busy Red Line allows maximum exposure to crush loads, as well as winter operation immediately adjacent to expressways like the Dan Ryan, which throw off salt and sometimes snow.

Both of those can damage the trains’ electric motors, which are mounted on the axles.

The CTA says the test phase will continue until transit agency officials and manufacturer Bombardier Transportation are satisfied.

The cars have undergone thorough, and successful, testing so far under all possible conditions.

The new 5000-series train cars have fewer total seats than the current ones, some of which have been in use since 1969. But most of the seats are center-facing like the train cars on the New York subway system, providing more standing space to pack in rush-hour commuters.

The new cars also have networked security cameras, an event recorder system and door sensors.

In another feature that takes a page from the New York subway system, the CTA system maps inside the trains have electronic displays showing the location of the train relative to the rest of the system.

The new cars are capable of going 70 mph, although for testing, they have been limited to the current 55 mph limit.

They were manufactured in Plattsburgh, N.Y., by Bombardier, which also makes cars for the New York, Boston and Toronto subways, among others.

A number of changes have been made since the cars debuted last year. A total of 396 more cars are on order, and the CTA is negotiating to buy an additional 300.