Speed during construction work

  • I came across today what seemed to me like a bug, but please explain if there is something I haven't read or understood about the game.

    I was to cross a track og construction work, limited to 40 km/h speed with my trains today. (Awful decision, but wanted the prestige.)

    My trains went from Manchester to Brussels. I had 11 Dionysos and 1 Morpheus. As we all know Dionysos have higher acceleration, but Morpheus higher top speed. Morpheus was therefore well ahead of Dionysos when it entered the track of slow speed. Then it virtually stood still. I thought this was because it had to start from 0 acceleration again, but obviously it quickly reached 40 km/h. Still the Dionysos caught up with the Morpheus and outran it by a few minutes.

    Was there a bug to my Morpheus running through that track?