what kind of wood for this

[chizlr40]

my boss has wants me to build some guide rails for a small wash unit at his dealership in michigan. the old ones are still intact but wore out due to 20 years of use. they are roughly 4x4 with edges cut off so as not to puncture any tires. they are constantly wet and subject to cars and trucks running over them. he went el cheapo last monday and whoever did it used construction grade pine. needless to say they have already fractured. i turned the job down because of what he wanted to spend,think almost nothing but would maybe make a recomendation on what type of wood should be used and if he comes up on the price i might do it. anyway what would be a good wood to use in these conditions. thanks for any suggestions or opinions

[edgy]

Black Locust would probably be my choice. I have fence post still solid after 40 years of wet/dry cycles, all just stuck into a hole in the ground with no sand or cement.

[oakey]

White oak will take quite a beating and stand some wet conditions
And it is relatively cheap and easily found here in michigan

[mike4244]

my boss has wants me to build some guide rails for a small wash unit at his dealership in michigan. the old ones are still intact but wore out due to 20 years of use. they are roughly 4x4 with edges cut off so as not to puncture any tires. they are constantly wet and subject to cars and trucks running over them. he went el cheapo last monday and whoever did it used construction grade pine. needless to say they have already fractured. i turned the job down because of what he wanted to spend,think almost nothing but would maybe make a recomendation on what type of wood should be used and if he comes up on the price i might do it. anyway what would be a good wood to use in these conditions. thanks for any suggestions or opinions

Both white oak and black locust are perfect if you can get them. White oak is probably easily accessible. I put a fence in for relatives in 1963 using black locust posts and rails. Pickets were cedar. The fence posts and rails are still original, pickets have been replaced at least twice. 
Both species are strong and will take a beating from tires rubbing . 
Don't let your boss take advantage of you. If the cheap $%^&* tries to knock down your price , then turn the job down.
mike