The incident took place at the Donnersbergerbrücke bridge which carries road traffic over the train lines.
British and US aircraft dropped 1.5m tons of munitions on Germany during the Second World War, and it is believed as much as 15 per cent failed to go off.
Around 2,000 tons of unexploded ordnance are still discovered each year, and Germans are used to large areas of cities being evacuated and cordoned off so they can be safely removed.
In 2017, 70,000 people had to be evacuated from their homes in the financial capital Frankfurt after an unexploded 1.4-ton British “Blockbuster” bomb was found.
In 2011, 45,000 people had to leave their homes in Koblenz when a drought exposed another Blockbuster bomb lying undetonated on the bed of the Rhine river.
In 2019 a 550-pound bomb that had lain undetected since the war went off in a field outside Limburg in the middle of the night.
The bomb was not disturbed and it is believed it went off because the chemicals in its detonator had decomposed.
No one was injured but the bomb registered 1.7 on the Richter scale and left a 13-foot deep crater.