Hi, have my class 1 booked next week. Having just seen a thread about a roll away situation, wanted to check I have my facts right…So, please correct:
I have read you always check park brake in cab and trailer brake is on before coupling up. I am not questioning this! So these are theoretical ‘should never happen’ questions about what actually happens if you get it badly wrong:
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If you leave unit park brake off, but trailer brake switch is on, when you connect the red line does the trailer remain braked because of the trailer brake switch? And in this situation it all could start moving when you turn off trailer brake? (and you should just put trailer brake back on and wait/hope?)
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If you leave unit park brake on, and trailer brake switch is off, then trailer brakes are on while nothing connected (as long as shunt not pressed), then you connect red line and trailer is braked because unit park brake is on? (so bad practice but usually not an issue)
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If you manage to have unit park brake AND trailer brakes switch off, and connect red line, entire outfit becomes unbraked? Best plan is to pull red line back out again if you can, returning trailer brakes (eventually) to service?
(Also I just wondered why has no one ever thought of having a trailer brake switch by the airlines as it would be much safer to hit that than try and pull out an airline if you have messed it up.)
Thanks! Looking forward to my training. Tim
th2013:
(Also I just wondered why has no one ever thought of having a trailer brake switch by the airlines as it would be much safer to hit that than try and pull out an airline if you have messed it up.)
Thanks! Looking forward to my training. Tim
Chances are it’ll get snagged by a suzzie when turning an slap your breaks on when turning.
Co-op have some trailers with the park / shunt button by the front of the fridge and I’ve only once caught it with a suzzie when shunting but anything’s possible.
The simple way is break check break check and CHECK ,
If you get interrupted when doing anything start at the beginning or 2 steps before you got interrupted and after it only takes a min to walk round to make sure its all done .
Think you getting your self worked up before you start…lol
Simple rule of thumb, never leave the tractor unit cab with out the park brake applied, weather it being running or not…
Id say its a basic requirement to check that the trailer brake is engage before attempting coupling up and the same when it comes to un -coupling to ensure the trailer brake is engage,
The whole concept is your not suppose to send the trailer flying back… 
you capture the trailer and tug twice to confirm capture… then its a case of safety clip on the kingpin, Susie lines, legs, dis engage the trailer brake and finally check your rear lights… :
Remember, once the trailer brake is dis engage the tractor units brake is the total vehicle brake
Think you getting your self worked up before you start…lol
To be honest I believe I know what you need to do (check and check again). I just like to know how things work…and WHY you have to do things…
Remember, once the trailer brake is dis engage the tractor units brake is the total vehicle brake
That doesn’t seem right… I thought that if Park brake is on in tractor unit then trailer brakes are also on (assuming airlines are connected) or am I missing your meaning? cheers
The curiosity is not a bad thing. But a little knowledge can, in this case, be downright dangerous. I am not being patronising when I suggest that you put your energy into just doing it correctly - every time.
There are various gadgets in use (eg warnings if you open the cab door without applying the unit park brake) which are great as long as they don’t lead to complacency.
Please don’t misinterpret my comments; I have a serious concern about folks getting this wrong. Some have died as a result.
Pete 
Thanks for reply. Please rest assured that I too take this very seriously and would never deviate from what I am taught.
It turns out that a book I purchased a while ago (“The official DSA guide to driving goods vehicles”) has a helpful section which answers my questions with sensible diagrams. Having read it I also realise that there is enough diversity between systems that generic answers would be at best misleading, at worst fatal.
So will focus on just getting it right, as suggested!
th2013:
Remember, once the trailer brake is dis engage the tractor units brake is the total vehicle brake
That doesn’t seem right… I thought that if Park brake is on in tractor unit then trailer brakes are also on (assuming airlines are connected) or am I missing your meaning? cheers
What he’s trying to say is that once the trailer brake is disengaged the only thing stopping everything rolling away is the unit brake. I think you’re both saying the same thing just in different ways.
Terry you got it in one but I think th2013 is looking at possible wild scenario and the what ifs…
End of the day do it as the instructors tell you, you wont go far wrong, its when you start cutting corners and getting lazy that’s when mistakes happen
Remember assumption is the mother of all screw ups and leads to accidents
Thanks for advice all, looking forward to the training!