GR Web FX 1 Junior Poster in Training

Hey People,

I am having some difficulty figuring out how to do a visualisation technique in Photoshop. Basically i work an engineering company who design Highways, and alot of work involves widening roads/increasing lanes.

I have a photo of a motorway which currently has 3 lanes which i would like to increase to 4 lanes. I have uploaded the image to www.proposedsite.co.uk/image

I have found it difficult because as the road goes into the distance the road obviously gets narrower due to perspective.

Does anyone know how i would go about realistically adding a new lane to this image or does anyone know of any tutorials specific to achieving this??

Thanks alot
GR Web FX