European Commission proposals that would force highway authorities to upgrade the safety design and signage on roads used for cross-border journeys may be illegal.
The proposals were part of new harmonised standards that aim to ensure major road networks throughout Europe were built and maintained to the safest standards.
However they could be illegal under European Union treaty laws, MEPs have warned.
The European Parliament transport committee has alleged that the tabled directive could break the key EU principle of subsidiarity, where policy issues are reserved for member states, unless expressly approved otherwise.
A committee statement also pointed out that the new system would create too much red tape.
While infrastructure improvements would save lives, “this is best achieved by allowing member states guidelines,” said the MEPs.