text: The A282 Northbound Junction 1a entry slip road now has a height limit of 4.8m,
  
  All traffic which joins at this slip road has to use the western bore of the Dartford Tunnel, which is subject to a height limit of 4.8m.  
  
  There is no option to 'crossover' any more, like there was previously.  Non-compliant vehicles are stopped by a Traffic Safety System (a system of signals and barriers) which identifies, stops and extracts non-compliant vehicles from the tunnel approach.  They are then forced to drive back to Junction 1b and approach the correct tunnel.