The cops stand under the Erin Mills overpass and catch with radar. They also sometimes stand under Erin Mills Parkway, but have other cop cars waiting behind (between after you come up the hill after the Mavis exit and the erin mills parkway). If you see a black car that looks like it might be undercover standing on the side of the road just as you’re coming up the hill (going westbound) towards erin mills, then you can be sure that there’s a radar ahead.