The officer's actions meant two cars had to slam on their brakes in the middle of the busy M8 motorway in Scotland.
One driver, who recorded the scary incident on his dashcam, can be heard saying: "F****** hell. Wow, wow," as he realises how close he came to a crash.
The footage shows traffic moving steadily along the road just after rush hour, before the police motorbike swerves across three lanes just moments after joining the motorway.
The car recording the clip, travelling at around 40mph, is forced to move to the right as the police bike moves in front with just inches to spare.
A dash cam clip from two minutes later, then shows six police motorcycles travelling two-by-two with two police cars following, further along the M8.
Police Scotland said the officer was "attending to his duties" but refused to give more details.
The video was recorded on Thursday, April 20 at 9.37am at junction 21, near Govan, Glasgow.
The footage starts as the dashcam vehicle drives in the outside lane amongst the steadily moving traffic.
A black Renault in the middle lane slams on its brakes as two police motorbikes come into view.
The first bike moves immediately across the inside lane and then shifts across the middle before edging over the lines into the outside.
The driver of the dashcam vehicle is forced to hit the brakes and lets out a sound of shock as they move to the right to avoid a collision with the police bike which pulled out inches in front of them.
Speaking about the incident, the driver of the dashcam vehicle who wished to remain anonymous, said: "There was absolutely no reason that I could see for this police biker to merge immediately into outside lane.
"Thankfully traffic was a little bit behind me otherwise there could have been a serious crash.
"You'll notice the other biker doesn't swerve as aggressively, and it clearly wasn't an emergency as they don't pass me until several minutes later."
"I drive a small red car and I personally think he didn't look properly and didn't see me."
A spokesman for Scotland’s Worst Drivers, who obtained the footage, said: "While the police biker had his blue lights on, he nearly ended up under the wheels of the dash cam car.
"Bearing in mind the road conditions were damp, by merging from the slip road across the entire carriageway was reckless.
“Clearly the driver of the dash cam car was not expecting him to do this either."
"It's concerning that a police officer would attempt such a manoeuvre in what was clearly not an emergency situation."
A Police Scotland spokesman said: "The officer was attending to duties and as such it would be inappropriate to comment further about this.
"If anyone wishes to complain about the police they can do so by visiting the Police Scotland website."