It's well known that alcohol affects our ability to drive.
It's well known that alcohol affects our ability to drive.

It's a major road safety issue.
It's a major road safety issue.

Drink driving is decreasing
Drink driving is decreasing

but the incidents of drug taking and driving is on the increase
but the incidents of drug taking and driving is on the increase

and the effects are little understood.
and the effects are little understood.

So the Transport Research Lab
So the Transport Research Lab

is assessing the effect of illegal drugs,
is assessing the effect of illegal drugs,

in this case cannabis, on driving.
in this case cannabis, on driving.

We're looking at cannabis
We're looking at cannabis

because we've just completed a three-year study
because we've just completed a three-year study

of drugs in fatalities and we found
of drugs in fatalities and we found

compared with a study we did 10 years ago,
compared with a study we did 10 years ago,

there's been a massive increase in illicit drug use
there's been a massive increase in illicit drug use

by a factor of about five or six
by a factor of about five or six

and the majority of that illicit use is cannabis.
and the majority of that illicit use is cannabis.

It's a sophisticated protocol.
It's a sophisticated protocol.

A double-blind, placebo controlled, cross-over design.
A double-blind, placebo controlled, cross-over design.

We first used a double-blind trial
We first used a double-blind trial

because this means that the participants
because this means that the participants

didn't know what dose they were receiving.
didn't know what dose they were receiving.

The double element means that the person giving them the dose
The double element means that the person giving them the dose

and anyone else associated closely with them in the trial
and anyone else associated closely with them in the trial

also didn't know what they were receiving.
also didn't know what they were receiving.

Thereby they couldn't contaminate them in any sense
Thereby they couldn't contaminate them in any sense

by influencing them in some way.
by influencing them in some way.

In one trial they were given a placebo
In one trial they were given a placebo

which looks real but has the active ingredient in cannabis
which looks real but has the active ingredient in cannabis

called THC removed.
called THC removed.

The placebo controlled element is very important
The placebo controlled element is very important

because people know they're part of an experiment.
because people know they're part of an experiment.

They have been given something but they don't know what.
They have been given something but they don't know what.

They're going to react in a particular way,
They're going to react in a particular way,

they maybe think they're getting something
they maybe think they're getting something

and if they're giving them nothing and they still react
and if they're giving them nothing and they still react

then this might look like an effect.
then this might look like an effect.

So you do want to compare them against giving them nothing.
So you do want to compare them against giving them nothing.

The cross-over design gives another level of control.
The cross-over design gives another level of control.

The cross-over trial in this context
The cross-over trial in this context

was used because we wanted to bring people in
was used because we wanted to bring people in

to give them four different doses of cannabis.
to give them four different doses of cannabis.

People vary hugely between themselves and vary less within themselves
People vary hugely between themselves and vary less within themselves

particularly with the sort of activities involved,
particularly with the sort of activities involved,

driving type activities, other laboratory experiments.
driving type activities, other laboratory experiments.

So we want a control for that sort of variation,
So we want a control for that sort of variation,

we want to reduce the variation.
we want to reduce the variation.

So we use them as their own controls.
So we use them as their own controls.

To do that we bring them in four times
To do that we bring them in four times

and we call that a cross-over trial.
and we call that a cross-over trial.

The participants were allocated to one of three groups.
The participants were allocated to one of three groups.

The groups being defined depending upon the dose order.
The groups being defined depending upon the dose order.

In other words participants in the first group
In other words participants in the first group

might have taken a placebo on the first visit,
might have taken a placebo on the first visit,

the low dose on the second visit and a high dose on the third visit.
the low dose on the second visit and a high dose on the third visit.

Participants in the second group might have started with a low dose
Participants in the second group might have started with a low dose

and participants in the third group with a high dose.
and participants in the third group with a high dose.

Choosing participants for this sort of trial
Choosing participants for this sort of trial

has got several tricky elements.
has got several tricky elements.

First and foremost we couldn't afford to use people who are naive
First and foremost we couldn't afford to use people who are naive

in terms of smoking cannabis.
in terms of smoking cannabis.

Use of naive people would be totally inappropriate.
Use of naive people would be totally inappropriate.

They have to be users basically.
They have to be users basically.

But of course smoking cannabis or possession of cannabis
But of course smoking cannabis or possession of cannabis

is an illegal act.
is an illegal act.

So we're looking for people who on a day-to-day basis,
So we're looking for people who on a day-to-day basis,

at least a weekly basis in our terms, were conducting an illegal act.
at least a weekly basis in our terms, were conducting an illegal act.

That's slightly tricky in terms of finding them.
That's slightly tricky in terms of finding them.

You can't just put an advert in the paper.
You can't just put an advert in the paper.

So what do you do?
So what do you do?

Virtually everybody you know
Virtually everybody you know

will know somebody who probably uses cannabis.
will know somebody who probably uses cannabis.

So that's the sort of route we took.
So that's the sort of route we took.

Do you think from the Ethics Committee point of view
Do you think from the Ethics Committee point of view

that would be completely acceptable?
that would be completely acceptable?

They'll want to see the way that we propose to run the study.
They'll want to see the way that we propose to run the study.

Who's going to be smoking what and when.
Who's going to be smoking what and when.

And how we're going to monitor it.
And how we're going to monitor it.

They're going to want to see that we're taking some safeguards
They're going to want to see that we're taking some safeguards

to ensure the health of the volunteers,
to ensure the health of the volunteers,

making sure that they won't come to any harm.
making sure that they won't come to any harm.

But they shouldn't do because they're already smoking the stuff.
But they shouldn't do because they're already smoking the stuff.

The researchers also screened participants
The researchers also screened participants

to prove they were regular cannabis users
to prove they were regular cannabis users

and were not taking other illegal drugs.
and were not taking other illegal drugs.

Once selected,
Once selected,

participants were monitored over the course of the experiment.
participants were monitored over the course of the experiment.