The possibility of a new cycle/walking route from Whittlesford station in part using funds from proposed adjacent development (Relocation of Welches transport depot from Stapleford/Shelford
The platform which is c 264m long extends beneath A505 overbridge.
Longest trains are 240m (12 coaches). This route was investigated some 10 years ago.
Greater Anglia say a route is not possible. I regard this as a stuck rather than locked door.
It may be possible with the use of a fence to take over all of last few metres or to have half (if half cyclist dismount signs may be needed)
As a very last resort to may be REQUIRED for those with bikes to walk.
I can see no reason why a walking route cannot be permitted.
Any 'risk' crossing A505 at grade must be orders of magnitude greater than using end of platform!