Network Rail's insurers are set to take a hit from the Charlton rail crash on Monday.
Marsh rail and bus expert Andy Brown said: "Potential claims for insurers could come through death and personal injury claims against the infrastructure owner if the train driver was not at fault."
Loss adjuster GAB Robins has been appointed by train operator First Group to assess the claim.
The crash involved the 7.03 First Great Western (FGW) train service from Hereford to Paddington which hit a minibus carrying farm labourers crossing the line.
Three people were killed and five injured in the minibus.
The labourers were reported to be Iraqi Kurds who were employed in the area to pick spring onions.
GAB Robins Rail Unit team leader Mike Marston said: "Early indications are that the minibus driver did not contact the signaller before crossing.
"The train did not derail and suffered only superficial damage."
Brown added that more risk assessment was needed on the 1,415 private rail crossings across the UK rail network.
"These crossings are tested regularly. The question has to be asked, when was the crossing last inspected?"
According to sources, FGW will probably claim against the insurer of the minibus. A GAB Robins spokeswoman said it was too early in the investigation to ascertain whether the minibus driver was insured or not.