You cannot under any circumstances use compression fittings to repair the lines on a public transportation vehicle. For example if you were rebuilding a car or repairing a car you might choose to use a compression fitting to repair the brake line.

Old Britts Braided Lines
Can you use compression fittings on brake lines. The cunnifer lines take compression fittings well. Similarly compression fittings are only allowed in vehicles that are not used for public transportation. The green coating usually needs to come off. For example if you are renovating or repairing a car you can choose to use compression fittings to repair the brake lines. Compression fittings on both style lines in trans and power steering lines. Some people argue that they are safe for use since they have already tried and tested them.
In addition compression fittings are known to leak when used on brake lines causing a loss in brake fluid and ultimately failure of the braking system. There have been a lot of controversies regarding the use of compression fittings for brake lines. Again it is only acceptable to use compression fittings in a vehicle that is not used for public transportation. There are essential things about a brake system you should know such as the issue about compression fittings. Compression accessories will be a temporary solution that allows you to complete other repairs or work on the vehicle. During temporary maintenance compression fittings can also be used to repair brake lines.
Trans cooler lines dont have much pressure but power steering sure does and theres been no problems with many miles and daily driver use. Many states have banned the use of this repair on passenger vehicles too. Compression fittings are also admissible to use on brake line repairs when the repair is temporary.