Police, bunkered down in bushland armed with high-powered lasers, recording equipment and military fatigues, are focusing their attention on the Black and Reefton spurs, past Healesville, notorious for dangerous driving.

Sergeant John Morgan, of the Yarra Ranges traffic management unit, said covert tactics used in Operation Surreptitious II were a way for police to make road users slow down without roadside speed cameras and patrols.

"Drivers and riders know if they speed, even if they don't see a camera, they will still be checked by police hidden in the bush, and picked up a couple of kilometres ahead."

Police impounded two motorcycles that were ridden at speeds of 137kmh and 141kmh, charged 15 people with speeding, including 12 riders and three drivers, and charged four with crossing a single white dividing line.

Similar operations last summer picked up 62 speeding motorists, resulting in 10 impoundments.

A strong police presence, including targeted operations such as Surreptitious I and II, Facade and Phoenix I and II, have resulted in fewer collisions and less impoundments in the past two years.

"These operations were initially implemented to combat the high number of motorcycle collisions; this trend has now turned around, and more cars are speeding through here."

In one hour of last Sunday's Operation Surreptitious II, the Journal saw police catch five motorists, and issue seven infringement notices.

All five motorists exceeded the 80kmh speed limit by more than 20kmh, and two lost their licence.

Sergeant Morgan was not fazed by motorcyclists spreading the word about covert policing, nor riders "doing laps" to try and spot the radar's positioning.

"We're happy to sit here all day and not catch anyone, as long as they slow down, they're reducing their likelihood of a crash. At the end of the day, if they're telling other riders about us and slowing down, they're doing our job for us - and saving lives. It's a win-win situation."

The Yarra Ranges last year recorded 15 fatalities. The region continues to top Traffic Accident Commission data for the past 20 years in serious injury collisions and fatalities.