If you are caught speeding, you might be offered the option of a speed awareness course, rather than taking the points on your licence. Harm reduction is the objective, making it less likely that you'll offend again.
Smart idea, and it often works. But what if there were no speed courses available and you had to wait a month, six months, a year, or more?
And what if the only way to get on that course was to keep on speeding, foot to the floor, putting yourself and others in mortal danger throughout the long waiting period?
Sounds completely crazy, right? But this analogy gives a small sense of the lethal absurdity that many heroin addicts in Belfast find themselves trapped within.
Here is how it happens. The person makes the decision to tackle their addiction: this can be an incredibly difficult, painful process, and many don't ever get to this stage.
They then discover they will have to wait at least 18 months before getting on to the Belfast Health Trust's substitute prescribing programme, a harm reduction initiative which weans them off heroin through the use of replacement drugs like methadone.
What choice are addicts left with, other than to keep on mainlining the deadly drug until the authorities finally decide they can provide the required treatment? According to the most recent figures, 44 people are currently trapped in this hell, with no immediate prospect of release.
Michael McDowell, from Belfast Experts by Experience (BEBE), a group for addicts and former addicts, says that these people are dying in slow motion. He has seen the evidence with his own eyes.
"I have a friend who has been on the waiting list for a year-and-a-half, and I have watched him physically deteriorate," says McDowell.
"He's gone from smoking heroin to injecting heroin and he has had numerous overdoses.
"His life is in danger every day."
McDowell buried another friend from BEBE just last week.
Anyone who thinks that this is a simple issue of personal responsibility and that giving up heroin is a matter of waking up one morning and renouncing the stuff - well, they need their own head examined.
Addicts should not be preached to, criminalised, punished or reviled. They should be given the necessary support to free themselves from the living nightmare of their addiction.
And support should be given promptly, as soon as the call for help is made.
Evidence shows if that call is ignored, or put off, the moment may be lost, and the user may slide into even more dangerous behaviour, beyond the reach of anyone's help.
So, why isn't treatment immediately available? Well, in some health trusts, it is. Outside Belfast, there are no delays, except for the Western Trust area, and its waiting list is tiny by comparison.
Michael McDowell does not accept the explanation that the long waits in Belfast are primarily down to difficulties with resources and funding.
He points out that the other health trusts deal with larger numbers and receive similar funding, yet manage to operate without significant delays.
Nobody is claiming that substitute prescription programmes are a panacea. Heroin-assisted therapy, in which the opiate is prescribed for use under medical supervision, as they do in Switzerland and Canada, is a far more effective (and cost-effective) treatment. But methadone substitution is better than nothing and it's desperately needed. We have a spiralling opiate problem in Northern Ireland which is rapidly getting out of control, and it is killing people.
Every year, on July 21, BEBE holds a memorial service at Crescent Park in south Belfast to remember those who have lost their lives.
It would be an outrage and a travesty if the names on that memorial roll were to increase, even by one, as a result of delays in providing treatment.
So what is going wrong in the Belfast Health Trust, and why is the wait for the substitution programme so disproportionately long?
While 18 months is the latest official statistic, Michael McDowell says that users have told him they have been on the list for much longer than that.
It is important that we know the answers to these questions and that urgent action is taken, because human lives are currently hanging in the balance.
Heroin users are often viewed with fear, contempt or suspicion.
But these are some of the most vulnerable people in society and their lives are no less valuable because they are addicted to drugs.