Here's one of my more complex mods. What you think its just dropping a prim? That's the easy part you can rez a light bar anywhere you have access to that option. As and Eternal Desires DJ i have that access. I get it because sometimes the host isn't on time and i can Rez Contest boards and giveaway boxes.
I digress. it seems easy to simply mount a light bar on a vehicle. its not that easy. you first rez the light then move it NEAR where you want to put it. you then use the edit tools to rotate it perfectly adjust the size and put it in place. to connect it to the Mesh vehicle you need a modifiable vehicle, you MUST highlight both parts. you MUST highlight the light bar first THEN the vehicle. Use the edit menu to link and SAVE the vehicle by Taking it from the world and re rezzing it. you then adjust the colors and sounds of the lights.
This Vehicle started out as the 777 Warg W/ GTFO, i used it's HUD to paint it . Once all the modding was done this was renamed the FDC Climber. It will enter the field as a High mountain and off road Unit. It SHOULD have Blue and Yellow lights. but it has red and yellow.