A man has died following a serious crash on the A414.
Police were called to a crash involving two cars, two vans and a lorry at 9am near the Park Street roundabout on the A414 North Orbital Road, St Albans.
Emergency services attended the scene and a man in his 60s was pronounced dead.
A 36-year-old man from Luton has been arrested at the scene on suspicion of causing death by careless driving. He is currently in police custody.
Sergeant Simon Cooper, of the Bedfordshire, Cambridgeshire and Hertfordshire Road policiing unit, said: "Despite the best efforts of the emergency services, a man sadly passed away at the scene.
"We have informed his next of kin, and they are currently being supported by specially trained officers.
"We ask that their privacy is respected at this difficult time."
A man, 36, from Luton was arrested at the scene on suspicion of causing death by dangerous driving, he currently remains in police custody.
The road is closed from M1 Junction 8 at Hemel Hempstead to the Park Street roundabout to allow emergency services access the scene.
Traffic on the M1 southbound is unable to exit the motorway and will have to come off the M25 clockwise and take the A405 northbound to St Albans.
Police say the road, which is shut in both directions, is likely to be closed for most of the day.
As a result, there is queuing traffic on the A414 and surrounding areas in St Albans, including Watling Street towards Chiswell Green.
Rachel Payne, from St Albans, said she heard a bang and then spotted the collision.
Ms Payne said "cars have been crushed" as she saw police tried to overturn the lorry.
People are asked to avoid the area, and advised to find alternate routes where possible.
Sergeant Cooper added: "We are appealing for the public's help so we can give them some answers.
"If you were driving in the area at the time, did you witness the collision of the events leading up to it?
"If you do have information and haven't spoken to us, please get in contact as a matter of urgency.
"If you were in the area and have a dash cam fitted to your vehicle, we ask that you please review the footage and send us anything you think could assist our investigation."
To report information, visit herts.police.uk/report or herts.police.uk/contact, call the non-emergency number 101 quoting Op Fermat, or altertnatively contact anonymously on 0800 555 111.
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