Take a look at Ion video cameras. I've used an Ion Speed Pro on almost every ride for more than a year. Shaped pretty much like the Contour Roam -- cylindrical, roughly like a largish headlight.

• Runs about 90 minutes per charge on video, up to 3 hours in time lapse still mode.
• Weatherproof as-is, no special housing needed.
• Only two controls, a large slider switch and press-button, easy to feel and operate without looking on a helmet mount.
• Can be run and charged simultaneously via external USB battery, but this compromises the weatherproof seal -- it's necessary to remove an O-ring sealed rear cap to access the USB port and other controls.
• Good daytime image quality; fair low light; mediocre nighttime IQ due to poor dynamic range.

Good value for the usual $50-$75 prices on Amazon and elsewhere. I keep hoping Ion will improve it with longer battery run time and better low light performance.

I'd also rather have a slightly less wide lens. The Ion is designed as an action cam for up close action. A traffic document camera lens should have less barrel distortion (nearly like a fisheye lens) and either better resolution of fine detail or a less extreme wide angle.