The last two times on my daily ride I stopped at a major intersection with multiple stop lights in both directions. Both times as I looked down at my computer the mph indicator was jumping around, today it went to 100 mph and stayed there until I was moving again. Then when I got home it showed I had gone about 2 miles further than I usually do on that route.
I haven't noticed it doing this anywhere else yet. Am I a bit crazy or could the changing lights at the intersection be throwing off my computer. Anyone ever heard of such a thing?

Wireless computer? They sometimes do strange things.

My wireless used to throw up speed's of 70 MPH when near my laptop.

Analog wireless is prone to that. It may not have been the stoplights themselves, but something else in that area. On my old analog cyclometer, turning on my headlights added 50 MPH to my speed.

Digital wireless systems seem not to have that problem.

Yeah, its wireless. Does not say if digital or analog.

Take a pic of the Max speed attained before you zero the days ride.

Best pic I could get...check this out though...when the red light on my wife's Nikon digital camera came on and illuminated the computer it started to dance around, just like at the stop light.

Ah! That's it. Your cyclometer is channeling Frosty the Snowman.

It's likely caused by the loop detector embedded in the pavement (the circle or rectangular cuts you see at intersections). The loop detector works by generating a magnetic field, and when metal (such as a car, or a bicycle wheel) comes within range, the light controller senses a change in the field, causing the light to trigger. A common side-effect is interference with wireless cyclometers.

My computer acts up when I ride by some airports. Everythings works fine except my HR monitor my max rate will spike to 260+.

Happens to me when I get too near a certain store. Top speed 75 mph? don't think so.

Same scenario-- My Vetta wireless does wierd things at traffic lights, and when my heart rate monitor showed my HR in the 200+, I almost had an "anxiety attack". I finally realized it was the traffic control devices that were causing the problem. My computer also shows a momentary rise in speed when I go under a set of power lines near my house.

LOL! ( Frosty, go to the light...go to the light..)

I think you were correct on this one...I sat a lane over at that stoplight today and no problems with the computer..Did notice that the lane I had been sitting in had the "cutout" for the detector.