It happened on the B3081 near Verwood - he had to be cut free by firefighters.
Hampshire & Dorset Police Welcome Legal Highs Ban
The South Coast's police forces have welcome a blanket ban on so-called legal highs which has come into force.
Laws criminalising the production, distribution, sale and supply of the drugs took effect from midnight.
Offenders will face up to seven years in prison under the Psychoactive Substances Act. It had been widely expected that the measures would be rolled out in April but the start date was pushed back. The legislation has come under intense scrutiny since it was first proposed by the Government last year.
There have been warnings that the ban could drive dealers on to the so-called ``dark web'' - unlisted websites that are difficult to trace.
Official analysis published last month found that deaths linked to so-called ``legal highs'' more than tripled in two years, with a total of 76 recorded in England and Wales over a decade from 2004.
A number of deaths of young people in Hampshire have been linked to the substances. They included schoolboy Adam Hunt from Southampton in August 2013 - five days after taking AMT and etizolam and falling seriously ill - and 19-year-old trainee doctor Doug Ferguson from Chandler's Ford.
Michael Lane, Police and Crime Commissioner for Hampshire and the Isle of Wight, said:
"I support the change in law around so-called legal highs. The suggestion that they are legal infers to people that they are safe. This change in the law, to make these substances illegal, removes that false perception and inference.
"These substances affect your behaviour, health, and are potentially lethal; they should be known as lethal highs because they can and do kill people. My priority is to keep residents safe and this change in law makes it clear that these are in no way safe."
The new law comes in less than two weeks after a 15-year-old boy, thought to have taken legal high Spice in Poole, was treated in hospital. Officers were called to the High Street at around 7.10pm on Saturday 14 May to reports that a boy had stopped breathing.
The boy was taken to hospital and has since been discharged.
Detective Inspector Garry Knight, from Dorset Police, said:
"Today, Thursday 26 May 2016, a blanket ban on the sale of psychoactive substances has come into force, outlawing the trade in so-called 'legal highs'. Dorset Police takes the enforcement of drug related laws seriously.
"Only the other weekend we had an incident in Poole which highlights that individuals taking such drugs could be putting their health and even their life in danger.
"I would strongly advise those thinking of taking any psychoactive substance to think again. You can't be sure what you're taking, and the side-effects are unpredictable and potentially nasty."
Violent crime was up 37% in the last year. Police say it's mainly due to a change in how offences are recorded.
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