My local police having been taking the more pragmatic approach of setting up detection stations at convenient places (such as on the slope of a hill with a tunnel exit with a good downwards/sideways view into traffic) or even hiring a party bus to cruise up and down busy roadways, with plain-clothes officers in the windows looking down into cars - and then radio-ing the license plate number to mobile units (usually a gaggle of police motorbikes stationed nearby) who pull over and ticket the offending drivers.