A 40,000-litre capacity tanker lorry carrying liquid hydrogen tipped over into a ditch on a curve in an intersection while travelling on a municipal road at the edge of town. The lorry had just left a SEVESO-rated industrial gas production plant.The cistern was retained by an electrical tower and did not completely overturn. A whitish cloud dispersed through the degassing chimney on top of the cistern. First responders set up a 200-m safety perimeter and evacuate the neighbours. The containers internal pressure remains at approximately 0.1 relative bar. The explosimeter measurements conducted at the degassing chimney outlet, at a height of 3-4 m, remained positive. At 2:30, fire-fighters extended the safety perimeter to 600 m and lifted the cistern, thereby allowing technicians with the transport company to access the cistern control box. Responders closed the hydrogen degassing valve, which had been slightly opened due to the shock produced by the accident. The explosimeter measurements then turned negative. Around 5:30 pm, the semitrailer was placed back on the road and escorted into the industrial gas production plant, which was equipped with a degassing unit. For the most part, the cloud was composed of liquid nitrogen used to maintain the hydrogen at a cold temperature. The inclined position of the cistern had caused the liquid nitrogen spillage. The cryogenic cloud dissipated thereafter.The Inspectorate visited the site. Given the presence of nitrogen protoxide storage, only empty semitrailers were allowed on the site. According to the operator, the lorry driver had come to the site of his own initiative, looking for replacement hoses. He accessed the site without waiting for the shift foremans approval and entered through the door that had not immediately closed following entrance of the previous vehicle. Realising that the tanker lorry loaded with liquid hydrogen had accessed the site without authorisation, the foreman asked the driver to back up. During the manoeuvre, the lorry bumped the gate. The foreman then requested he exit the site by the rear; in advancing along this path, the driver missed a turn. Nitrogen protoxide production resumed 3 days later.The Inspectorate noted a procedural problem in the industrial sites safety management system (SMS), as the vehicle filled with liquid hydrogen should never have allowed accessing the site. Inspectors requested that the site operator issue a report analysing the causes of this incident. A follow-up inspection was ordered to ensure that new organisational measures had indeed been implemented as part of the operators Safety management System.