Here's What Actually Happens When An Ambulance Goes Into 999 Mode

I’m going to be completely honest with you here ― I didn’t think much about what happened to ambulances when they got a 999 call until I read a Reddit post shared by site user u/deadliftbear. 

Yesterday, they asked members of r/AskUK: “What happens when an ambulance is put into 999 mode?” 

They explained that they’d been “watching Ambulance on BBC One and notice[d] that every time they go on lights and sirens, the onboard computer says ’999 mode activated.’” 

A top-voted comment underneath reads, “In the services I’ve worked for the 999 mode button turns on the blue lights and ‘arms’ the siren, meaning it will now activate when pressed.”

“In most cases the steering wheel horn activates the siren however in some cases a button elsewhere, such as a stalk is used for this,” they wrote. 

But is that true?

Yep, basically 

HuffPost UK spoke to Mark Brickhill, Managing Director at O&H Vehicle Conversions (one of the UK’s largest manufacturers of ambulances and other emergency vehicles) about the topic.

“Selecting ’999 mode’ activates sirens and blue lights and disables the ambulance’s auto-control speed restrictor,” he confirmed.

“When the ambulance arrives with the patient it switches to ‘at scene’ mode which enables the paramedics/crew to take the keys and leave the vehicle locked but the engine keeps running with emergency lights still flashing,” he continued. 

“This ensures that the ambulance systems in the rear continue to function ― including seasonal air conditioning and heating ― ready for the patient if transport to the hospital is needed.  

 “If this is the case, “999 mode” is usually redeployed until arriving “at hospital” mode where the engine continues to idle to support the ambulance equipment in the saloon, but without blue lights.”

A Reddit commenter, u/UkSmurfy, added that “A single press turns on the primary ‘wailer’ siren used for transmitting sound long distances, subsequent presses will cycle through sounds such as the two-tone siren or ‘phaser’ which sounds like crazy high pitched alternating noise used for helping people nearby pinpoint our location.”

A paramedic previously confirmed to LADbible that UK ambulances use three sounds; a faster and slower “nee-naw,” then a tri-tone, which sounds more like a wibble. 

“We also have a bullhorn which is used for certain situations,” she told the publication.

Different ambulances use different systems, of course. 

Sounds... loud

“I hear the radio in my sleep and wake up... I then get in the car and head to work...” a commenter wrote. 

Another Facebook user asked under the post what 999 mode really does, to which the response was much the same; it “just turns the blue lights on,” a paramedic replied, while another responded “and siren power. If your vehicle speed is restricted, it also removes this. Our vehicles are restricted to 72 without the 999 function.” 

The more you know...