Air brake question

[fireman]

Newbie here. How much air pressure is carried in the brake line of a modern freight train?
Thanks in advance.

[slashmaster]

90 pounds, and I believe through the decades it has slowly gotten higher.

[locomotive112]

Back in the early 1940's ( I stop there on my RR studies) the freights used 70psi and the passenger trains used 90psi.

[Shirehorse]

As slashmaster said, it's 90 psi.

90 PSI for road, yard, and transfer.

110 psi for passenger service.

[Engineer Spike]

Many roads use 75 or 80 psi for yard an transfer. This serves two reasons. First it is quicker to charge. The second has to do with brake pipe gradient. That is the difference in pressure between the engine and the last car. The switch engine may add cars to the rear of a train. This train may have a gradient of 10 psi. When the cars added, and charged to 90 psi. The cars added would be overcharged by 10 psi. This may cause sticking brakes, or other problems.

[10more years]

just to add a little more information and background: Even in the 80's, CSX used 90 pound air for road freight and 80 pound for yard jobs. Just personal opinion and experience, but brake pipe gradient is probably not as much issue as in times past. It still is a consideration, but freight car control valves have gotten better, train lines are better, and train line leakage (overall) is better. I get a lot of trains where rear car pressure is within 2-3 pounds of the locomotive pressure. I don't remember exactly when, but they went to 90 pound for all freight sometime in the early 90's .

[CN_Hogger]

I can't recall the exact rules, but some heavy mountain grade territory use of 100psi for freight is required.

I agree with trainline leakage being better these days. My longest train to date, 197 cars and over 2.25 mi long was able to maintain 87psi on the rear!

CN_Hogger