Use soft-edge yellow-white brush to create headlight glow.
step 3 of 4
Used smaller soft-edge brush on a new layer and placed circle in middle of each headlight glow, then used motion blur @ 300px to create the diagonal 'lens flare' effect. Used soft eraser to make the flare less uniform.
step 4 of 4
On a new layer, using the same brush but much larger (~400px), painted in front of cars to give illusion of the road being illuminated. Set layer blend mode to 'Overlay'.