Make a copy of the layer containing the pillar and choose after that Free Transform option to place the copy as it demonstrated below:

Create a new layer and apply here a standard brush of black color to represent the shadow under the road sign:

The parameters for the layer containing the shadow: Fill 40%

On the next new layer (Create new layer) apply the standard brush of black color (Opacity 20%) to represent a kind of attrition effect on the panel and the pillar:

Insert the appropriate text on the road sign:

Find a picture with the police car on it:

Cut out the car, inserting it on our main picture:

Download the Grungy Paper textures, one of it being chosen for our collage:

Use the next demonstrated parameters for the layer containing the paper texture: Blending mode-Linear Light

Press on the same layer CTRL+U

Finished!

View full size here.