First, a comment on tail lamps. Until about the eighties it was a requirement for every train to carry a separate tail lamp to show to signalmen it was complete. I believe this is now only a requirement for trains unable to display high intensity lighting.
Regarding the Heljan railbus, as others have said, an excellent looking model. Running seems a pot luck issue. My mate had one running round the club layout in each direction, from a crawl to a prototypical looking top speed for about 2 hours. My own, I tried a couple of days later with different results. From a good crawl it ran jerkily up to about half speed, in either direction. Further running didn't improve matters. I'd noticed the plates by the wheels and commented at the club that with the weight plus 2-axle drive it could earn its keep hauling a train!.
Anyway the plates were removed and revealed a lot of thick grease amongst the gears. This was part of the problem with Heljan's class 17 'Clayton' loco causing it to run slow. So I cleaned out most of the grease, put it together but no better. Believing the grease may have got to the motor bearings, I set about gaining access to the motor. The instructions mention checking motor oiling without actually telling you how to get to it. It requires the removal of every screw you can see (all 17 I think!) plus light guides. This releases the upper body half, cast roof weight, interior, lower body half, cast upper chassis half and cast lower chassis. Between these last two is the motor held snugly in recesses in the castings by 2 'O' rings. Each end of the motor is a cone shaped flywheel running closely in similar shaped recesses in the chassis castings. Here lay the problem!, the copious grease was all around the flywheels and in what little clearance there was, preventing the motor reaching full speed. I cleaned it all up, put it together, ran it, and for a short while it seemed ok, then it started to slow down. Subsequent investigation revealed the damage had been done with the motor burning out. This, after discovery of the suppressor chokes in the 21 pin blanking plug having failed.
Hope this of help to anyone else.
Jim.