Stopping for Police
Judging by the result, it may be a significant event in many driver's lives to be pulled over by the police. I've seen everything from jamming on the brakes and stopping in the middle of the lane to following oblivious drivers for many kilometers before they caught sight of my emergency lights. The tendency was closer to the former rather than the latter, although some drivers made it quite plain that my choice of a place to stop them was not a good one.
In most cases, I would turn on my emergency lights and catch up to the vehicle that I wanted to stop. I would then follow along behind until the driver noticed me and pulled over. If the spot they chose was not a good one, I would ask that they move to a safer location and finish the contact with them there.
The choice of where to stop was really theirs because I was signalling them to stop. The law requires that they immediately come to a safe stop and the safe stop qualifier allows some leeway in the driver choosing to find an appropriate place to pull over depending on the circumstances.
If it was really important that the driver stop regardless, I would turn on my emergency lights and siren. The additional use of the siren removes the driver's discretion in choosing to do anything more than immediately moving to the nearest edge of the roadway clear of an intersection and coming to a full stop.
Where we ended up was entirely my responsibility to deal with.
The presence of an emergency vehicle should not come as a surprise to any driver unless their ability to see is limited by the character of the highway. Being aware of traffic other than that directly in front of you allows a defensive driver to act in anticipation rather than react in panic or not act at all. It would probably also have reduced the complaints about me having picked a lousy place to stop someone as well.