Fireworks operators need more training on how humidity and bonfire smoke can mix and cause reduced visibility on roads and railways, a coroner has said.
West Somerset coroner Michael Rose has been investigating how seven people died on the M5 at Taunton in a pile up minutes after a bonfire event was held.
Mr Rose also said fog detection devices and overhead gantries to warn people may have prevented the crash.
His report has been sent to relevant public bodies and the government.
He called for a risk assessment which "took into account the topography of the area, nearby watercourses and prevailing wind conditions" while "identifying highways and all other matters relevant for the safety of onlookers and nearby residents".
Humidity, wind speed and direction needed to be checked immediately before the display, the report said.
Other recommendations included fireworks operators having licences.
However, calls made by the bereaved families for a minimum distance between firework displays and main roads have not been included in the report.
The inquest in April concluded the firework smoke was not to blame for causing the crash, but the coroner said he could not rule out the possibility that smoke and fog had mixed and reduced visibility on the motorway.
Geoff Counsell, the organiser of the fireworks display, was cleared of a health and safety offence last year.
The crash happened in November 2011 near junction 25 of the M5 in Somerset soon after a fireworks display at Taunton Town Football Club.
The report has been sent to the Department for Transport, the Health and Safety Executive and the Department for Business Skills and Innovation.
All parties now have 56 days to respond.