is there any way to make the lettering / stripes on police cars reflect like they do in real life on the cars when lights like head lights shine on them

outside of having to use  ENB and ICE somehow

Check out Double Doppler's BPM pack. He put like circles in his vehicle colors and it helped the reflection in my game. I dont have anything other than a realistic time cycle/ 

It really depends on the contrasting colors and shades are blended with each other, and how good your ENB/ICE/Timecycle brings them out. Stealth liveries look good at night (if done correctly), and textures with reflective attributes/designs also work well.