Has anyone ever done lighting effects with a police car to make them flash alternately?

I tried to do this without any success, I used the point light and the spot light but I couldn't see the results after the rendering, any help would be greatly appreciated.

You could ...

Animate the lights using the "Constant" function and turn each light ON then OFF alternately.

cheers,
dr geep
;=]

Thanks I will try that... which lights would be better to use, the point or the spot light?
by the way I like your Poser University...

I would use a Point light inside the physical light (object) on the police car and
turn OFF (uncheck) "Casts shadows" for the physical light (object(s)) on the police car.

Glad you like the"U" .......... it's a work in progress ... ;=]

cheers,
dr geep
;=]

Point lights flashing as the good doctor mentioned would do the trick.

If you want a really dramatic animaed effect you can use spot lights and rotate them alternately, like when one is at y rotate 0 position, another is at y rotate 90. 

Actually I would parent them to the physical light objects and rotate those physical objects for the proper look.

The moving shadows produced can give an added dramatic effect to a crime scene animation for example.

@ SYNTRIFID

Good suggestions ... perhaps a little more difficult to implement but certainly would provide much more dramatic shadow effects in the scene.

Summary ============================================

Blinking Lights - Use Point lights and turn on/off

Rotating lights - Use Spotlights as suggested by SYNTRIFID

===================================================

cheers,
dr geep
;=]

There are a variety of nodal solutions for flashing lights, this is probably the simplest.  The rate is controlled by value 1 of the sin node. This is set to change every 2 frames. Flip the step for the other light. (default) You can use the same function on the ambient value of a prop to make it flash. (Just in case we are talking about alternating headlamps instead of alternating lights)