Much of the improvement is credited to a focus on clearing traffic before it reaches the border. In March, 200 cars typically were awaiting border clearance every day. Today, the daily average is 58 cars, KCS says.

Transit times have been reduced by one or two days, meaning a car moving from any point on KCS or Tex Mex reaches Monterrey or Mexico City in six or seven days.

And on-time performance is better than 90%, KCS says.

KCS and Tex Mex pre-block Mexico-bound trains, and use the KCS yard at Bossier City, La., to stage traffic that hasn't been cleared for the border crossing at Laredo. The yard at Beaumont, Texas, continues to stage Mexico-bound traffic originating in the Beaumont and Lake Charles, La., areas, however.

Each day, KCS originates train AJAMX, consisting entirely of Mexican-bound traffic, from Jackson, Miss., to Bossier City. At Bossier City, all cars that have not been approved for clearance into Mexico are removed from the train, and it is pre-blocked to interior destinations in Mexico.

The train carries three Mexico blocks when departing Bossier City: Mexico City, Monterrey, and a mixed block for other destinations. Once the train is blocked at Bossier City, it departs directly for Beaumont, where it makes one final pick-up of previously cleared and blocked cars. After the train departs Beaumont it bypasses all terminals on Tex-Mex and can operate directly over the border.