I set the speed limit at 40 mph from point A to point B. At point B there is a station with a limit of 15 mph. The consist will only go 29 mph, all signals show green. When I set the limit at 45 mph at point C the consist will go 33 mph. At 35 mph it goes 25 mph. My power is a 8-40b and a gp60 with 20 cars behind not loaded. Any ideas or suggestions as to what is going on? Thanks.