Traffic evaporation: are you serious?

Some reflections on shopping, the school run, filters, and the possibility of actual and significant traffic evaporation.

Last night I attended the first of the information sessions for the consultation on the Green Lanes Area Transport Study, and I am afraid I was not always patient. While some people become less temperate when sitting alone at a computer keyboard, but I become more so – I am better able to edit myself. So if any of the project staff who were present at the event reads this, please accept the apologies of the tallish middle-aged American bloke who was exasperated that a large study of traffic has almost nothing to say (except on the one case of Wightman Road) about traffic reduction, and limits its analysis with the assumption that the overall number of car trips is fixed.

I am an economist, and, while economists disagree with one another about many things, our fundamental starting point is that people make choices between alternatives.  It is therefore hard for me to think of any activity like the choice to drive as fixed: I think of it as something that rises, or falls, depending on the relative attractivenes of driving and of alternatives to driving. When I look at the problem of traffic, I am asking myself what made this person or that decide to take a trip in a car, rather than walk or take the bus or just stay home, and what change in the situation might lead to a change in their transport choice or their decision to make the trip. Most people in Harringay choose not to travel by car, and the number making that choice can change for various reasons.

There are many filtered roads – roads where through car traffic is prevented, usually by bollards or gates – in Haringey as in other London boroughs. Hackney has a particularly large number, more all the time. Waltham Forest is installing a lot of them, as part of its mini-Holland programme, and because they’re part of that programme – meant to be a model for other London councils – the effect on traffic of those filters is being studied. As I mentioned in a recent blog, studies from the first neighbourhood in the programme (Walthamstow Village) show traffic reductions on the newly filtered roads –former rat-runs – of over 90%, small increases on the adjacent main (unfiltered) roads, with an overall reduction in traffic for the area of 16%. That is a serious reduction. But how, and why, could something like that work in the Harringay Green Lanes area?

People who drive cars on a daily basis usually do so for one or more of three reasons: getting to work, going shopping, and taking kids to school. These aren’t the only reasons, and of course they don’t include the important category of people who drive for (rather than just to) work, but they cover most trips by most people. What I’m discussing here is two of those: shopping, and the school run, as examples of how traffic evaporation can work.


One of the big generators of traffic in the Green Lanes area – perhaps the biggest – is the Arena shopping park, a planning abomination which is fortunately scheduled to be demolished when its lease runs out in the early 2020s. Among its attractions are a large Sainsbury’s and a McDonalds with a 24 hour drive thru.

As an expatriate American I suppose having a 24 hour McDonalds at the foot of my road should make me feel warm all over, with memories of hot summer nights, road trips, and other heartstrings that the memorabilia on the walls of Banner’s in Crouch End are trying to tug as I write this. But it doesn’t really float my boat, and when I walk by, my thoughts switch between outrage at the exhaust fumes my son and I are breathing and thoughts about the health effects of repeated doses of Big Mac and Coke taken without ever leaving the car. I’ll be glad when the whole thing goes. For now, though, let us ignore the longer-term collective choices that are embodied in planning decisions, and instead focus on immediate individual choices about whether or not to drive to Sainsbury’s; Sainsbury’s here could just as well be Homebase or any other store in the Arena shopping centre.

People have lots of ways of getting groceries. In the Green Lanes area, they can drive to Sainsbury’s, or they can walk or cycle or take the bus there, or walk (I won’t keep repeating “or cycle or take the bus”, but you can fill it in) to Tesco’s little less-than-a-superstore on Green Lanes near St Ann’s Road; they can walk to one of the many independent grocery stores in Green Lanes, where there is not only a wealth of choice in the Cypriot / Eastern Mediterranean line, but a growing range of Polish, Hungarian, Italian and East Asian food, and of whole/organic food; they can get deliveries to their home; they can hop on a bus to Wood Green or Finsbury Park and go to Lidl, or to Morrison’s in Wood Green where I understand the fish is better than at Sainsbury’s. And, for each of these choices, they can decide how often to do it. How people choose to share their shopping out among these different locations and modes of transport depends on many things in their daily schedules, their cooking/dietary habits, what they forget when making shopping lists and the size of their refrigerators. All of these factors stack up differently for different people and they make different choices. If you make driving to Sainsburys somewhat less convenient or more time consuming, or if you make walking or cycling feel a bit safer or more pleasant, some people will decide not to drive so often to Sainsbury’s but to get their groceries some other way (at another store, or walking to Sainsbury’s or driving to Sainsbury’s less often) .

Some of the traffic reduction measures which residents requested at various phases of the consultation would cut certain routes to and from the Sainsbury’s – one such proposal was for filters (bollards) on each Ladder road, which would have blocked the certain favoured routes from Wightman to Sainsbury’s via Green Lanes; another was for cutting through traffic on north-south routes linking West Green Road and St Ann’s, which would have made drivers from the north of that area go to Green Lanes by some longer route if they wanted to reach Sainsbury’s by car. How would such changes these affect the amount of car traffic to Sainsbury’s? We don’t know: because of the multiplicity of alternatives, and of personal factors involved in the choices, it is impossible to know in advance.

However, for either set of filters, you can be nearly certain of two things: that fewer car trips to Sainsbury’s would take place, and that some of the car trips that did take place would now be a bit longer(*). The first of these means less traffic, the second means more; so, again, we don’t know for certain whether the overall effect would be to reduce or raise the kilometres driven on Harringay’s roads. But, given the range of shopping and transport choices people have available to them, it would be very surprising if the result were not less traffic overall to and from Sainsbury’s.

One thing that needs to be borne in mind when talking about the considerable traffic going to the big Sainsbury’s is that superstores like that are yesterday’s news, anyway: the big supermarket chains are expanding their businesses in home delivery and small shops (Tesco Metro and so on), and overall are also losing ground to chains like Lidl, which for Harringay purposes is best accessed by bus. Moreover, car ownership in London has been falling for years. Discouraging people from driving to Sainsbury’s is pushing on an open door.

The school run

School run traffic can pose particular problems at the school gate: unloading at zig-zags or other inappropriate places, drivers keeping the engine idling while they wait, congested traffic or speeding traffic in places where children are arriving at school by foot or bike. Many schools, and many councils, make efforts to manage the school run by controlling these behaviours, restricting traffic in certain areas around the school at drop-off and pick-up times, and urging parents to get their children to school in some way that doesn’t involve driving to the school gate. All of these are worthy, and are probably what the consultation Steering Group had in mind when it said that the problem is unique to each school and requires a bespoke solution at each, with the support of the school community and the neighbours.

But we need also to see that school run traffic affects people beyond the school gate and, even more important, that motor traffic encourages the school run.

My son is in year 5 at Chestnuts Primary School. He, his mother and I discuss now and then the conditions under which he would (the day keeps getting postponed) be allowed to walk or cycle to school on his own. At the risk of sounding like the old fogey I suppose I am, when I was his age I cycled two and a half miles to school any day I didn’t feel like taking the school bus, and if I had taken the bus in the morning I could walk home when the mood struck. So I regard my son’s transportation situation as a sad one and an unhealthy one, and I know from the parents of his friends that it is a common one. There are, of course, various dangers a child may encounter on the streets, but talking with other parents the biggest factor is traffic. Some of that traffic is school run traffic, most of it probably is not.

You can make a lot of school run traffic evaporate by providing safe routes for kids walking or biking to school. Or, to put that slightly differently, by providing routes that will on average lower the age at which parents are willing to let their children get to school on their own. For parents who aren’t ready to let their kids go alone even on a traffic-free route, you can further reduce the school run by making driving less convenient, or walking or cycling more pleasant, for the parents. The fastest and cheapest way to accomplish these objectives is to do what many people want done anyway – to filter traffic off of secondary roads that cut through the neighbourhoods near the schools. Let me return, then, to my favourite sets of hypothetical traffic filters, on the roads of the Ladder, and the north-south routes between West Green and St Ann’s.

Take the Ladder first. There are two big schools on the Ladder, North Harringay and South Harringay. Both draw most of their pupils from the Ladder, and both are located on the Passage, a pedestrian route which runs the length of the Ladder. I think it is indisputable that if there weren’t rat runs down the Ladder roads, more children would walk or cycle to school down the Passage, and fewer parents would drive their children to these schools.

The area between West Green and St Ann’s has more schools: St John Vianney, West Green, Woodlands Park Nursery and Children’s Centre, Chestnuts, St Ann’s CE, and Seven Sisters. If through traffic were eliminated on the north-south routes through this area, far more children would be able to walk or bike to school. Combine that with some improved pedestrian crossings of St Ann’s & West Green, and you’re there.

I need to say, too, that consideration of schools brings to the fore the problem of air pollution. We are all aware that pollution – from gasses like NO2, and from particulates of various sizes, disproportionately from diesel vehicles but also from tyre and brake wear of all motor vehicles, is now seen to be a significant public health problem, shortening the lives of people living in this city and in particular children growing up in it. Traffic is not simply a problem of roads that are clogged, but of health. It is a problem of health both because it discourages active travel, and because it fouls the air. To add one more school, and one more rat run, to the mix, St Mary’s, on Hermitage Road near St Ann’s, has very traffic, difficult conditions at school run time (hard to cross the busy road), and bad air quality. A filter somewhere on the system linking that end of Hermitage Road to Seven Sisters Road, would solve the problem.

The two work together

Summing up: filtering traffic out of these neighbourhoods would have several advantages: making the streets quieter and the air cleaner, and encouraging active travel by facilitating safe routes to school.

What they also reduce traffic congestion or overall traffic volumes? We can’t know for sure without trying.  In the case of the West Green-St Ann’s this experiment would require investing in a number of bollards or gates, and a few cameras (the cameras are to allow buses but not cars down Black Boy Lane). In the case of the Ladder there would need to be a two-stage experiment, the first to test placement of the filter along one or more of those very long roads, and to figure out just how to handle turn-around of cars and trucks; the second stage would apply the solution found in the first phase to the rest of the Ladder roads (though the northernmost five roads are different, and can be pretty well taken care of with a single filter or gate, at Frobisher Road and Green Lanes).


(*) There is another possibility, which is that filters, by simplifying the traffic system, will make traffic flow better, leading to more trips but with less congestion. This is known as Braess’ paradox, and the traffic patterns in and around the Ladder are seen by many as a good candidate for this. Whether you would like that outcome would depend on whether your objection to traffic is (i) overall volume, (ii) traffic on residential roads, vs. main roads, or (iii) congestion. If this did turn out to be a Braess’ paradox situation, filtering traffic would not reduce overall traffic (item i), but would still quiet the filtered residential roads (ii), while reducing congestion on the unfiltered roads (iii).


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