same aspects may set a speed limit depending on what they are. the intention is that the line speed be re-established at an appropriate point to let the trains know when to resume speed after they have passed the point the signal intended the speed limit. for instance, you dont want a train doing 70 mph on a crossover between 3 tracks, the signal would set the limited, medium, or restricted speed and then a lineside speed sign should set the speedlimit back once the train has cleared. this is typical of speed signals and their operations in trainz. one possible cause would be the signal displaying incorrect aspects by not having it's path set properly in the properties dialog. in the real world, the rules normally call for the train to resume speed once the interlocking or control point is cleared (which is why the working length counters in my cabs come in handy).