Running Before We Can Walk.
Adapted from ‘Walkable City’ by Jeff Speck.
Introduction
It is easy to look back at the track record of our profession and conclude that our greatest failure was to provide the infrastructure that allowed all of us to welcome the private car into our lives with such relish. It is possible to believe that the profession picked the private car all by itself as the answer to everyone’s problems and set-about building our towns and cities around them before anyone else realised the damage that was being caused. But this view ignores the prevailing public opinion and available knowledge at the time. As the Government report, Traffic in Towns, eloquently put it back in 1963:
Before very long a majority of the electors in the country will be car-owners. What is more, it is reasonable to suppose that they will be very conscious of their interests as car-owners and will give them a high priority. It does not need any gift of prophecy to foresee that the Governments of the future will be increasingly preoccupied with the wishes of the car-owners.
Given the information available and the political climate it is hard to see how the transport profession could realistically have come up with anything else. Certainly, any notion of car traffic and the resulting congestion finding some sort of naturally occurring balance seemed like a long way off:
No doubt there is some ultimate degree of congestion, far worse than anything we know at present. Lack of a garage, or other place to house a car, can sometimes be a deterrent to ownership of cars but probably only in the very centre of large cities. There is little evidence that congestion of traffic stops people from owning cars and trying to use them, and that is perhaps the fact of greatest relevance.
But the costs associated with the rise of the private car were equally apparent to the profession:
It may be that future generations will regard our carelessness in allowing human beings and moving vehicles to use the same streets, and our apparent callousness to the inevitable results, with the same horror and incomprehension with which we recall the indifference of earlier generations to elementary sanitation.
The hard truth is that this was and continues to be a cost that society as a whole is willing to shoulder in return for the perceived benefits that came with it:
We are nourishing at immense cost a monster of great potential destructiveness. And yet we love him dearly. Regarded in its collective aspect as ‘the traffic problem’ the motor car is clearly a menace which can spoil our civilisation. But translated into terms of the particular vehicle that stands in our garage (or more often nowadays, is parked outside our door, or someone else’s door), we regard it as one of our most treasured processions or dearest ambitions, an immense convenience, an expander of the dimensions of life, an instrument of emancipation, a symbol of the modern age.
Given the public’s overwhelming support, I would suggest that our professions greatest failure has not been our unsuccessful attempts to accommodate everyone who wants to drive a car. Rather, it has been our inability to act upon the substantial body of evidence that now exists which clearly points to the futility of our efforts. Furthermore, we have been even more spectacular in our failure to communicate this futility to the general public.
More specifically the profession has shown a complete inability to account for people adapting their behaviour to changes in their surroundings. And it is precisely this assumption – that human behaviour can be treated as a constant, regardless of design – that accounts for the ineffectiveness of so much standard practice.
If you work in transport then you will invariably spend your time attempting to resolve at least one of the following three issues; congestion, parking and safety. And this is hardly surprising given that most of the public complaints one hears about revolve around these three topics. So it stands to reason that any good public servant would work to improve them. But it is exactly these three areas where traffic engineering seems to get its interventions most wrong.
Congestion
Possibly the best known example of this failure to account for human behaviour is called Induced Demand. It is a phenomenon that every thoughtful traffic engineer seems to acknowledge, yet almost no one is willing to act upon.
It stems from the fact that whether we own or lease a car, most of the running costs are fixed: the price of the vehicle (and/or financing), the driver’s insurance, the registration fees, and most of the maintenance fees are largely the same whether we drive a little or a lot. The roads, bridges, and policing are largely paid for by general taxes from drivers and non-drivers alike.
This all adds up to a situation in which, once you have a car, you are paying to drive whether you drive or not, and in which the more you drive the less each mile costs. The result is that, once you own a car, there is very little stopping anyone from driving except for one important exception – congestion.
Congestion is the greatest constraint to driving. This is the one place where people are made to feel the pinch in their automotive lives. In fact congestion is the only thing keeping driving in check. This is why attempts to relieve congestion are almost always in vain. In 2004, a meta-analysis of dozens of previous studies found that on average, a 10 percent increase in lane miles induces an immediate 4 percent increase in vehicle miles travelled, which climbs to 10 percent – the entire new capacity – in a few years.
This happens because an increase in highway capacity momentarily reduces journey times, suddenly making driving more attractive and causing more people to drive. This negates any reductions in congestion. This outcome is known as Induced Demand.
The mechanism behind this phenomenon is simply a combination of invitations and human behaviour, which came to a head for many cities in the 20th century. In every case, attempts to relieve traffic pressure by building more roads has generated more traffic and more congestion. The volume of car traffic almost everywhere corresponds directly with the scale of available highway infrastructure to the point where cities actually need congestion to keep driving in check.
Despite the overwhelming evidence in support of this, the need for more highway space continues to be justified in terms of reducing congestion to improve journey times.
Parking
Unsurprisingly, parking works in much the same way. The main difference is that the costs associated with parking are often removed from the equation altogether. Because parking is so plentiful and often free to use, it is easy to imagine that its provision costs very little. But this is not the case.
When we shop in a store, eat in a restaurant, or see a movie, we pay for parking indirectly, because its cost are included in the price of merchandise, meals and theatre tickets. We unknowingly support our cars with almost every commercial transaction we make, because a small share of the money changing hands pays for parking.
Nobody can opt out of this. People who walk, cycle, or take public transport are subsidising those who drive. In so doing, they are making driving cheaper and thus more prevalent, which in turn undermines the quality of walking, cycling and public transport.
Worst of all is under-priced on-street parking, as this is essentially no fairer than giving random discounts on other municipal services like water or electricity based upon who circles around looking for a space the longest, and is just as counter-productive.
And like highways in general, all of this free and under-priced parking contributes to a circumstance in which a massive segment of our national economy has been disconnected from the free market, such that individuals are no longer able to act rationally. Or, more accurately, in acting rationally, individuals are acting against their own self-interest.
Even in cities with high residential densities and great public transport systems, ample parking encourages driving that would not occur without it. As the ‘Godfather of parking’, Donald Shoup likes to say “Off-street parking requirements are a fertility drug for cars.”
This subsidy could perhaps be justified if it produced some greater good for society, but it only produces one benefit: cheaper parking. In terms of other important measures it worsens air and water quality, speeds global warming, increases energy consumption, raises the cost of housing, decreases public revenue, undermines public transportation, increases traffic congestion, damages the quality of the public realm, escalates suburban sprawl, threatens historic buildings, weakens social capital, and worsens public health, to name a few things.
Safety
As with both congestion and parking, too many engineers fail to comprehend that the way they design streets will have any impact on the way that people use them. By their logic, just as more lanes can’t cause more driving and more free parking won’t generate more car trips, wide, empty streets won’t lead to high speeds.
Most traffic engineers, often in the name of safety, continually redesign city streets to support higher-speed driving. This approach is so counter-intuitive that its strains credulity: engineers design streets for speeds well above the posted limit, so that speeding drivers will be safe – a practice that, of course, causes the very speeding that it hopes to protect against.
Once again, decisions to widen streets, increase forward visibility and install guard railing to make them more forgiving are based on the assumption that, in so doing, human behaviour will remain unchanged. Such a requirement makes perfect sense in a world in which design can’t affect behaviour, but most motorist’s drive the speed at which they feel comfortable, which is the speed to which the road has been engineered.
Widening a city’s streets in the name of safety is like distributing baseball bats to deter crime.
Conclusion
In recent years there has been a push to encourage traffic engineers to consider the wider role of streets beyond that of traffic movement and to ‘design’ streets with a consideration for their potential as places. As well intentioned as this might be, trying to get traffic engineers to understand design seems a little futile when, as a profession, so much of their core output is so fundamentally flawed.
Some may think that it seems a bit unfair to blame the traffic engineer for this situation. After all, they are only doing what they have been asked to do. This would be acceptable if their current efforts to reduce traffic congestion, mandate minimum parking standards and attempts to improve safety didn’t wreck cities and perhaps also if they worked. This is particularly unforgiveable when you consider the substantial body of empirical evidence that now exists which quantifies the professions failures.
What traffic engineers should be telling people is that we can have the kind of city we want. We can welcome cars in the proper number and at the proper speed. We can be a place not just for driving through, but for arriving at.
It is easy to look back at the track record of our profession and conclude that our greatest failure was to provide the infrastructure that allowed all of us to welcome the private car into our lives with such relish. It is possible to believe that the profession picked the private car all by itself as the answer to everyone’s problems and set-about building our towns and cities around them before anyone else realised the damage that was being caused. But this view ignores the prevailing public opinion and available knowledge at the time. As the Government report, Traffic in Towns, eloquently put it back in 1963:
Before very long a majority of the electors in the country will be car-owners. What is more, it is reasonable to suppose that they will be very conscious of their interests as car-owners and will give them a high priority. It does not need any gift of prophecy to foresee that the Governments of the future will be increasingly preoccupied with the wishes of the car-owners.
Given the information available and the political climate it is hard to see how the transport profession could realistically have come up with anything else. Certainly, any notion of car traffic and the resulting congestion finding some sort of naturally occurring balance seemed like a long way off:
No doubt there is some ultimate degree of congestion, far worse than anything we know at present. Lack of a garage, or other place to house a car, can sometimes be a deterrent to ownership of cars but probably only in the very centre of large cities. There is little evidence that congestion of traffic stops people from owning cars and trying to use them, and that is perhaps the fact of greatest relevance.
But the costs associated with the rise of the private car were equally apparent to the profession:
It may be that future generations will regard our carelessness in allowing human beings and moving vehicles to use the same streets, and our apparent callousness to the inevitable results, with the same horror and incomprehension with which we recall the indifference of earlier generations to elementary sanitation.
The hard truth is that this was and continues to be a cost that society as a whole is willing to shoulder in return for the perceived benefits that came with it:
We are nourishing at immense cost a monster of great potential destructiveness. And yet we love him dearly. Regarded in its collective aspect as ‘the traffic problem’ the motor car is clearly a menace which can spoil our civilisation. But translated into terms of the particular vehicle that stands in our garage (or more often nowadays, is parked outside our door, or someone else’s door), we regard it as one of our most treasured processions or dearest ambitions, an immense convenience, an expander of the dimensions of life, an instrument of emancipation, a symbol of the modern age.
Given the public’s overwhelming support, I would suggest that our professions greatest failure has not been our unsuccessful attempts to accommodate everyone who wants to drive a car. Rather, it has been our inability to act upon the substantial body of evidence that now exists which clearly points to the futility of our efforts. Furthermore, we have been even more spectacular in our failure to communicate this futility to the general public.
More specifically the profession has shown a complete inability to account for people adapting their behaviour to changes in their surroundings. And it is precisely this assumption – that human behaviour can be treated as a constant, regardless of design – that accounts for the ineffectiveness of so much standard practice.
If you work in transport then you will invariably spend your time attempting to resolve at least one of the following three issues; congestion, parking and safety. And this is hardly surprising given that most of the public complaints one hears about revolve around these three topics. So it stands to reason that any good public servant would work to improve them. But it is exactly these three areas where traffic engineering seems to get its interventions most wrong.
Congestion
Possibly the best known example of this failure to account for human behaviour is called Induced Demand. It is a phenomenon that every thoughtful traffic engineer seems to acknowledge, yet almost no one is willing to act upon.
It stems from the fact that whether we own or lease a car, most of the running costs are fixed: the price of the vehicle (and/or financing), the driver’s insurance, the registration fees, and most of the maintenance fees are largely the same whether we drive a little or a lot. The roads, bridges, and policing are largely paid for by general taxes from drivers and non-drivers alike.
This all adds up to a situation in which, once you have a car, you are paying to drive whether you drive or not, and in which the more you drive the less each mile costs. The result is that, once you own a car, there is very little stopping anyone from driving except for one important exception – congestion.
Congestion is the greatest constraint to driving. This is the one place where people are made to feel the pinch in their automotive lives. In fact congestion is the only thing keeping driving in check. This is why attempts to relieve congestion are almost always in vain. In 2004, a meta-analysis of dozens of previous studies found that on average, a 10 percent increase in lane miles induces an immediate 4 percent increase in vehicle miles travelled, which climbs to 10 percent – the entire new capacity – in a few years.
This happens because an increase in highway capacity momentarily reduces journey times, suddenly making driving more attractive and causing more people to drive. This negates any reductions in congestion. This outcome is known as Induced Demand.
The mechanism behind this phenomenon is simply a combination of invitations and human behaviour, which came to a head for many cities in the 20th century. In every case, attempts to relieve traffic pressure by building more roads has generated more traffic and more congestion. The volume of car traffic almost everywhere corresponds directly with the scale of available highway infrastructure to the point where cities actually need congestion to keep driving in check.
Despite the overwhelming evidence in support of this, the need for more highway space continues to be justified in terms of reducing congestion to improve journey times.
Parking
Unsurprisingly, parking works in much the same way. The main difference is that the costs associated with parking are often removed from the equation altogether. Because parking is so plentiful and often free to use, it is easy to imagine that its provision costs very little. But this is not the case.
When we shop in a store, eat in a restaurant, or see a movie, we pay for parking indirectly, because its cost are included in the price of merchandise, meals and theatre tickets. We unknowingly support our cars with almost every commercial transaction we make, because a small share of the money changing hands pays for parking.
Nobody can opt out of this. People who walk, cycle, or take public transport are subsidising those who drive. In so doing, they are making driving cheaper and thus more prevalent, which in turn undermines the quality of walking, cycling and public transport.
Worst of all is under-priced on-street parking, as this is essentially no fairer than giving random discounts on other municipal services like water or electricity based upon who circles around looking for a space the longest, and is just as counter-productive.
And like highways in general, all of this free and under-priced parking contributes to a circumstance in which a massive segment of our national economy has been disconnected from the free market, such that individuals are no longer able to act rationally. Or, more accurately, in acting rationally, individuals are acting against their own self-interest.
Even in cities with high residential densities and great public transport systems, ample parking encourages driving that would not occur without it. As the ‘Godfather of parking’, Donald Shoup likes to say “Off-street parking requirements are a fertility drug for cars.”
This subsidy could perhaps be justified if it produced some greater good for society, but it only produces one benefit: cheaper parking. In terms of other important measures it worsens air and water quality, speeds global warming, increases energy consumption, raises the cost of housing, decreases public revenue, undermines public transportation, increases traffic congestion, damages the quality of the public realm, escalates suburban sprawl, threatens historic buildings, weakens social capital, and worsens public health, to name a few things.
Safety
As with both congestion and parking, too many engineers fail to comprehend that the way they design streets will have any impact on the way that people use them. By their logic, just as more lanes can’t cause more driving and more free parking won’t generate more car trips, wide, empty streets won’t lead to high speeds.
Most traffic engineers, often in the name of safety, continually redesign city streets to support higher-speed driving. This approach is so counter-intuitive that its strains credulity: engineers design streets for speeds well above the posted limit, so that speeding drivers will be safe – a practice that, of course, causes the very speeding that it hopes to protect against.
Once again, decisions to widen streets, increase forward visibility and install guard railing to make them more forgiving are based on the assumption that, in so doing, human behaviour will remain unchanged. Such a requirement makes perfect sense in a world in which design can’t affect behaviour, but most motorist’s drive the speed at which they feel comfortable, which is the speed to which the road has been engineered.
Widening a city’s streets in the name of safety is like distributing baseball bats to deter crime.
Conclusion
In recent years there has been a push to encourage traffic engineers to consider the wider role of streets beyond that of traffic movement and to ‘design’ streets with a consideration for their potential as places. As well intentioned as this might be, trying to get traffic engineers to understand design seems a little futile when, as a profession, so much of their core output is so fundamentally flawed.
Some may think that it seems a bit unfair to blame the traffic engineer for this situation. After all, they are only doing what they have been asked to do. This would be acceptable if their current efforts to reduce traffic congestion, mandate minimum parking standards and attempts to improve safety didn’t wreck cities and perhaps also if they worked. This is particularly unforgiveable when you consider the substantial body of empirical evidence that now exists which quantifies the professions failures.
What traffic engineers should be telling people is that we can have the kind of city we want. We can welcome cars in the proper number and at the proper speed. We can be a place not just for driving through, but for arriving at.
