Rampa (1/28/2019)
Start with a cone that has no bottom. So you'll need to import one.
Make it tall and thin.
align the point just in front of the light.
Set the material black, and the opacity to 1 (basically invisible)
Set the specular really high.
The light will shine on the specular cone and make a nice beam. It's also great for street light, and has the benefit of disappearing when the light is off.
I have used this methodology many times to create "beams of light", for table lamps, floor lamps, street lights, flashlights, etc.; You can even change the color of the beam to represent halogen versus incandescent versus fluorescent, etc. (see the difference in scene image below).
I use a cone shape that is topless & bottomless. However, I use a base color for the diffuse which is in the same palette as the glow map color. I also often use a normal map to create striations. The attached zip file has a cone example & some additional glow maps. Also, adding & attaching a point light to the "beam" can add additional realism.