Targets both N & Sbound. Northbound, I detected radar at 541 interchange( it was found to be North, 1/2 -1 mile away)and lifted throttle at 72MPH (traffic flows at 70). Officer was next seen (beyond overpass)in S.bound lane and then turned across divider to pursue N. He explained that I was picked because I was "in the lead". Later, I realized that remark was because he could not see me when the reading was made (overpass and uphill-downhill obscures his view). The ticket was for 83MPH, which was bogus. Also, at that distance the radar beam is far wider than all lanes.