the first continuous cab signal systems, eventually settling on pulse code cab signaling technology supplied by Union Switch and Signal. In response to the PRR lead, the ICC mandated that some of the nation's other large railways must equip at least one division with continuous cab signal technology as a test to compare technologies and operating practices. The affected railroads were less than enthusiastic, and many chose to equip one of their more isolated or less trafficked routes to minimize the number of locomotives to be equipped with the apparatus. Several railways chose the inductive loop system rejected by the PRR. These railways included the Central Railroad of New Jersey (installed on its Southern Division), the Reading Railroad (installed on its Atlantic City Railroad main line), the New York Central, and the Florida East Coast. Both the Chicago and North Western and Illinois Central employed a two-aspect system on select suburban lines near Chicago. The cab signals would display "Clear" or "Restricting" aspects. The CNW went further and eliminated the wayside intermediate signals in the stretch of track between Elmhurst and West Chicago, requiring trains to proceed solely based on the 2-aspect cab signals. The Chicago, Milwaukee, St. Paul and Pacific Railroad had a 3-aspect system operating by 1935 between Portage, Wisconsin and Minneapolis, Minnesota. As the Pennsylvania Railroad system was the only one adopted on a large scale, it became a de facto national standard, and most installations of cab signals in the current era have been this type. Recently, there have been several new types of cab signalling which use communications-based technology to reduce the cost of wayside equipment or supplement existing signal technologies to enforce speed restrictions and absolute stops and to respond to grade crossing malfunctions or incursions. The first of these was the Speed Enforcement System (SES) employed by New Jersey Transit on their low-density Pascack Valley Line as a pilot program using a dedicated fleet of 13 GP40PH-2 locomotives. SES used a system of transponder beacons attached to wayside block signals to enforce signal speed. SES was disliked by engine crews due to its habit of causing immediate penalty brake applications without first sounding an overspeed alarm and giving the engineer a chance to decelerate. SES is in the process of being removed from this line, and is being replaced with CSS. Amtrak uses the Advanced Civil Speed Enforcement System (ACSES) for its Acela