No Auckland motorist needs to be told how much parents taking their children to and from school contributes to traffic congestion. As much is underlined during school holidays when movement around the city becomes relatively easy.
Various schemes, such as the Travelwise and Bikes in Schools programmes, have sought to wean parents and pupils from their cars. None has made a substantial impact. All the more reason, therefore, to welcome the Green Party's policy to encourage pupils to walk or cycle to school.
As its starting point, this promising initiative acknowledges that parents are driving their children to school because they are worried that walking and cycling are not safe. This fear has sparked a dramatic change.
Twenty-five years ago, more than half of children cycled and walked to primary and intermediate schools, and a third were driven.
Today, these numbers are reversed. The outcome, according to Transport Agency data, is that one in three car trips in the morning rush is related to education.
The Greens' solution is to spend $200 million over four years on building cycle lanes and walkways around schools. Funding for this would be redirected from roading projects which they say, justifiably, enjoy too great a slice of transport infrastructure funding.
Safety would be much enhanced by ensuring cycle lanes were completely separated from busy or high-speed roads, and installing traffic-calming devices near schools.
Funding for such improvements would come from the Transport Agency, which would assess plans for walking and cycling developed by schools and their local authorities.
The Greens estimate that if walking and cycling returned to 1989 levels, 100,000 cars would be removed from the road each morning.
The biggest impact would, obviously, be felt in Auckland. It would also be the biggest beneficiary of reduced carbon emissions.
But all parts of the country stand to benefit from a drop in the rate of child obesity. A third of this country's children are said to be overweight. A daily walk or bike ride to and from school would supply exercise and help children stay healthy. The Greens are even able to cite Danish research that found walking or cycling to school boosted a child's ability to concentrate throughout the morning, to a level of a child half a year older.
Annual spending of $50 million is, as the Greens suggest, a drop in the bucket - just 3 per cent - of the transport budget. That appeals as money very well spent, given the scale of traffic congestion in Auckland.
Indeed, even more could be done. During last year's mayoral campaign, John Minto suggested free and frequent public transport would go a long way towards solving the problem. That is impractical. But cheap school-bus fares would surely be a reason to leave the car in the garage.
The Greens envisage half of children walking or cycling to school by 2020. Achieving that target would depend in large measure on schools and local authorities recognising the proposal's potential.
Schools have plenty of reasons to act. The clogging of streets outside their gates is as much a nuisance to them as it is to motorists trying to run the gauntlet. And the health and wellbeing of their pupils is their primary concern. From any number of angles, the Greens' policy makes sense.