Assessing the Effects of Operating Regimes on Track   - Railway Track and Structures
MINNEAPOLIS, Minn. –Operating practices on North American railroads have changed within recent years. Precision Scheduled Railroading (PSR) and its variants, which have been adopted by most of the Class 1 railroads, have led to changes in train lengths and speeds. In some cases, railroads are running shorter and faster trains; in most cases, they’re running longer, heavier, and slower trains.
Source: rtands.com