I wonder why they are not used any more? It was so much easer to attach the red line with a tap on the line!
Because the tap could inadvertently get caught up in a suzie and turned off while in motion.
Because drivers…
Would sometimes forget to turn the taps on or worse, only turn the red line on.
Used to be handy for transferring diesel to another vehicle or a can (@Conor they were my own motors before you ring the police 
) as shown to me by a Middle East ‘vet’'.
Also if you popped a red line you could still move it off the road and not be stuck there.
As Harry says the biggest problem was sometimes the taps would catch the line, and knock off, but a replacement with some kind of button would have sorted that.
Suppose it was like everything else, proven methods changed to a different system for no apparent reason other than for the sake of it with the jury out on whether it was an actual step forward or not… a bit like mirror cams and plastic steps and bumpers. 
There would be some justification for fitting a tap to the red line, fail to turn the tap on and you arn’t going anywhere.
I’d be wary of having a tap on the service line though, and depends on which make of vehicle you drive if it would be of any benefit.
My own opinion is that it would be too easy to drive off with the service line tap still closed.
Never had any issue personally with suzy lines closing taps, but having used palms (old style that were vey loose and had no safety clip) it was easy for a palm coupling to disconnect itself on tight turns, which you might be unaware of until you heard an unwelcome hissing noise when you next used the footbrake, thankfully still the days of the blue auxilliary line so the dead man or initial pull of the park brake would operate the trailer brakes independently…silly decision dumping the secondary brake system in my opinion.
Fitting lines easily when pressurised is a devise your own techique thing really, arm and hand pressure alone can be difficult for some so devise your own method of using your legs or the weight of your body to provide the main pushing force when connecting lines up, you can help yourself a lot by lubricating the connections, but then i’ve worked with people who would rather struggle and heave and kick Scania (especially) drivers doors open umpteen times a day instead of squirt some oil or spray grease in the hinges so chances of lubing the suzy connections? nil, not my job mate 
Harry Monk:
Because the tap could inadvertently get caught up in a suzie and turned off while in motion.
^ It was also easy to knock it off when moving around the catwalk or even forget to turn it back on after coupling.
Palm couplings are the best compromise for ease of use.
I second the technique suggestion. I use my knee against the back of my hand and push with my leg.
My foot is against the suzie bracket on the cab. Means I use my leg strength to do it. Makes it very easy.
I admit to being one of those that forgot to turn the taps on… once but never again. Luckily I wasn’t loaded very heavy and had plenty of room to stop, but it was an arse clencher all the same. 
trevorking1964:
I second the technique suggestion. I use my knee against the back of my hand and push with my leg.
My foot is against the suzie bracket on the cab. Means I use my leg strength to do it. Makes it very easy.
Its not so easy when you have a close coupled trailer, especially with a fride trailer.
A tap on the red line would be in my view a good idea, it can be safe gauarded with a lock of some sort or placed out of the way.
However how do you forget? The trailer won’t move if you don’t put the red line on and if your turning on the red line then you do them all don’t you?
Macski:
trevorking1964:
I second the technique suggestion. I use my knee against the back of my hand and push with my leg.
My foot is against the suzie bracket on the cab. Means I use my leg strength to do it. Makes it very easy.Its not so easy when you have a close coupled trailer, especially with a fride trailer.
A tap on the red line would be in my view a good idea, it can be safe gauarded with a lock of some sort or placed out of the way.
However how do you forget? The trailer won’t move if you don’t put the red line on and if your turning on the red line then you do them all don’t you?
Its precisely because it will move that the service and/or secondary taps could be forgotten and get out onto the road whereas forgetting the emergency just means it wouldn’t move.Its obviously a lottery which of the three taps got forgot possibly even both the blue and yellow together.
From memory don’t think we had taps after the change to two line.
Macski:
trevorking1964:
I second the technique suggestion. I use my knee against the back of my hand and push with my leg.
My foot is against the suzie bracket on the cab. Means I use my leg strength to do it. Makes it very easy.Its not so easy when you have a close coupled trailer, especially with a fride trailer.
A tap on the red line would be in my view a good idea, it can be safe gauarded with a lock of some sort or placed out of the way.
However how do you forget? The trailer won’t move if you don’t put the red line on and if your turning on the red line then you do them all don’t you?
Fair comment. Not a problem I’ve had yet. Still in my first class 1 job and we don’t have any trailers that are close to the unit as you mention.
Carryfast:
Macski:
trevorking1964:
I second the technique suggestion. I use my knee against the back of my hand and push with my leg.
My foot is against the suzie bracket on the cab. Means I use my leg strength to do it. Makes it very easy.Its not so easy when you have a close coupled trailer, especially with a fride trailer.
A tap on the red line would be in my view a good idea, it can be safe gauarded with a lock of some sort or placed out of the way.
However how do you forget? The trailer won’t move if you don’t put the red line on and if your turning on the red line then you do them all don’t you?
Its precisely because it will move that the service and/or secondary taps could be forgotten and get out onto the road whereas forgetting the emergency just means it wouldn’t move.Its obviously a lottery which of the three taps got forgot possibly even both the blue and yellow together.
From memory don’t think we had taps after the change to two line.
Where i worked at the time with palm couplings, they were only on the red and service line, the blue had a large male/female socket about half the size again of current connectors.
Biggest issue came when either we pulled other company’s trailers on socket connectors or vice versa they pulled ours, by the time you’d made up adaptors to suit all the connectors were at least a foot long.
To be fair, the only difficult to connect modern sockets are those that never see any lubricant, but you already know what they’re going to be like because when you approach the motor in question not only will it be filthy dirty with a good likelihood of several bulbs out, but the drivers door lock and hinges will be on the point of seizing through lack of anyone giving a crap, ditto the fifth wheel will have large swept sections devoid of any grease
Lubed now and again it’s no bother for anyone reasonably able bodied to fit the sockets.
peterm:
I admit to being one of those that forgot to turn the taps on… once but never again. Luckily I wasn’t loaded very heavy and had plenty of room to stop, but it was an arse clencher all the same.
Guilty m’lud…
Picked up a Scaac trailer out of Pompey docks and for whatever reason only turned the red line on. As I nearly drove into the back of another trailer at the exit gate, I knew exactly what I hadn’t done.
Lord it was close!
I can larf about it now.
205:
My first thought when i saw this post was this0
Me too
It maybe only a rare safety event - BUT if you have to stop going up on a hill/mountain covered in ice and the parking brake only works on the drive axle, even with chains on the whole rig can slide backwards.
A quick shut off on the red line can apply all the brakes and slown down or stop the slide before you can apply Brit chocks :- 4"x4" timbers with nails or factory fitted ready for use supplied with Euro motors.
whisperingsmith:
It maybe only a rare safety event - BUT if you have to stop going up on a hill/mountain covered in ice and the parking brake only works on the drive axle, even with chains on the whole rig can slide backwards.
A quick shut off on the red line can apply all the brakes and slown down or stop the slide before you can apply Brit chocks :- 4"x4" timbers with nails or factory fitted ready for use supplied with Euro motors.
Another example of why the three line system was best, in those circs you’d just apply the dead man and the rest of the outfit’s brakes would be applied.
It’s a right pain trying to get enough purchase to get the red line on under the body. There is also a selection of nasty rams, hooks and other things designed to smash your head in!
Edit. Even worse when this way up!
I always thought that having several valves linked together so one lever worked them all was the answer, with the lever having a gate on it like an in cab parking brake.
I imagine the amount of drivers injured or killed because of airline tap misuse equates to those killed by seagulls, but some no mark got it pushed through legislation.
Simply turning off the taps didn’t apply the brakes, you still had to break the connection.