Just to set the scene the section of motorway I was on had continuous road works for many miles so the "hard shoulder" had become one of the driving lanes
I was wearing a blues shirt, rather tight black trousers , grey Tommy Hilfigger briefs and black shoes
I was very tired so I stopped at a Service Station where I had a wee and consumed a bottle of Coke (which has a very strong diuretic effect on me!!)
Half an hour later I hit the back of a traffic queue, I was aware that there had been a bad accident up ahead, which had closed the whole motorway except the hard shoulder, however at this point I had no idea it was going to take me 2 hours and 20 minutes to travel the 7 miles to the next service station!!
Within about half an hour I bladder seemed to be filling really quickly, 15 minutes later things had got to the painful stage and I was starting to panic!!
The traffic would move a few feet and then stop and so on, I was also behind a lorry so it was difficult to judge how far we were from the next Services
15 minutes later I was beyond desperat, and had to resort to undoing my tight trousers and constantly holding myself through my underwear, frantically scissoring my legs whenever the car was stationary, I was also having o stand up in my seat whenever the car was not moving to take the pressure off my badly distended bladder
After what seemed like a lifetime I reached the "Services 1mile" sign, I cannot describe how happy this made me, however that just took my desperation to a whole new level!! ( that so near so far thing?"
From this point to reaching the services took another 30 minutes, eventually I was on the exit lane however the traffic was now queuing to get into the car park!!
Eventually I literally abandoned the car in the first space I found and got out of the car...now I had to do my trousers up...
I should point out that I am naturally quite shy and the idea of not doing up my trousers was not an optio ,however trying to do up tight trousers (which also had an internal button) was not the easiest thing with a bulging bladder! After what felt like an hour this was done, and then I tried to run, however this was impossible, I had to walk across the car park almost bent double as fast as I could, finally I reached the building entrance door and effectively hit a jam of people trying to get in and out, that was when I felt the first massive spurt hit the front of my undies and then another and another..
Fortunately the toilets were close to the entrance, however t my great Shame and embarrassment I was now having to hold myself through the front of my trousers to stop myself totally wetting myself!
The toilets were not large by motorway service station standerds and were unsurprisingly very busy, with a couple of lorry drivers chatting and shaving st the sinks as I frantically hobbled past, holding myself for dear life...
Fortunately there was one free urinal, however as soon I let go of the front of my trousers, I started pissing a long slow weak stream, my usual method of urinating is to fully undo the front of my trousers however there simply wasn't time for this, so I had to frantically fished my pissing **** out of my trousers and then properly let go, I would like to say the relief came instantly, however it was a full 2 minutes before the flow subsided with another 30 seconds of spurts and dribbles...
A very embarresed but relieved me walked back to my car in wet underwear and damp trousers with a still very sore tummy to continue my journey
Clearly even the biggest bladder has its limits!!
In the past I've slogged along endlessly in a traffic jam like that, finally reaching the service area, and although I was not as desperate as you I saw some people who were! 
