I want to have a train in my map so I am using the Flatbed Rail Carriage from dod_argentan.

I have placed a flat brush on top of the model to act as the floor of the carriage. However once you get onto the train and you are standing/running on the brush you can not jump. It's as if your feet are stuck in the brush.

Anyone got any ideas as to why this may be and how I can work around it?

I tried placing a player clip brush below and above the brush that is acting as the floor of the train but that did not work?

This should work fine. But one thing you could try if it wont work is making a brush the same size as the train, texturing it nodraw and then selecting not solid in the traincars properties.