Driving Motor Car 7091

Although taken in low light conditions, it is possible to make out a couple of modifications to this unit.
Just below the roof line towards the cab front window is visible a plate which has been attached to the front of the car. These are gradually being fitted to all the D78 units. The purpose is to strengthen the cab front at this point. 
Also note the pale grey roof.  This finish has also been applied to a number of units - its purpose is unknown to me, though it appears to wear better than that previously used.