The B1464, which runs in south Basildon between Pitsea and Vange, was closed to enable to lorry to be moved
The trailer has been left balanced on two wheels after hitting the bridge on the B1464 High Road in Pitsea, Essex.
Network Rail tweeted a photograph of the lorry using the hashtag "lorriesdontlimbo".
The company said High Road had been closed to enable the lorry to be moved, and trains were being diverted via Tilbury.
"Please check the height of your vehicle and don't chance it." A spokeswoman said: "We're working with Essex Police to free the lorry.
"Once this has been achieved we will carry out an inspection of the bridge to confirm that everything is safe before the road can be reopened and the rail line returned to line speed."
Train operator c2c said on its website that "due to a road vehicle colliding with a bridge between Basildon and Pitsea [railway stations], trains have to run at reduced speed on all lines".
It said services may be cancelled or delayed and the bridge strike was likely to affect "services running across the whole c2c network".