TOWARDS A NEW HIERARCHY OF ROAD DESIGNS: From Traffic Volume To Human Function

Streets were once the public space between buildings – available for any purpose that people wanted to use it for:  commerce, walking, horses, playing, standing, and anything else.  But over the past decades, one of the largest physical assets owned by the public was turned over for the exclusive use of “motordom.”  Streets became tubes for car traffic.  Transportation Engineers became road designers and developed a sophisticated hierarchy of street types – from Highways to Local Streets – intended to maximize the efficient movement of as many cars as fast as possible.

But what if street design was structured around functionality – not for cars but for people?  Instead of maximizing throughput volume they’d be designed to maximize the opportunity for people to participate in the full range of activity of the surrounding neighborhood.  It would require that the new road design slogan of being “context sensitive” began to be taken seriously, with the “context” being social and commercial interaction rather than vehicle access and mobility to the surrounding structures.

This would not require the elimination of the automobile, which (in the absence of viable alternatives) serves many vital needs for large segments of our population and businesses.  But it would require fitting car needs into a more balanced menu of human and commercial priorities.  And it might require transportation planners to work with – or even under – architects or other professions with deeper expertise in designing space for human activity.

In that case, perhaps the road design categories would include “mixed use” and “residential” and “Vulnerable Users” as well as “Connectors” and “Highways.”  And the key differentiation among the categories would be the way they facilitate non-motorized use of the public right of way at different times of day and year by controlling vehicular speed and parking.



As the new book Fighting Traffic points out, it took a concerted, expensive, and viciously fought campaigns spanning many decades for the automobile industry to transform our cultural assumptions about the proper purpose of roads.  The fact that cars were big, powerful, and dangerous gave an aggressive edge to their arguments that everyone else should stay out of their way.  Underpinning their success was the fact that this new technology opened powerful new economic opportunities for important groups and satisfied broad social desires.  (The triumph of “motordom” created enormous growth opportunity not just for car manufacturers but also for oil, steel, plastics, coal, rubber, real estate, construction, lumber, and other industries in nearly every part of the nation; while also giving people access to a wider world through increased personal mobility and freedom.)

Transportation engineers think of streets in terms of the amount and speed of the traffic they are designed to carry.  Over time, they developed a hierarchy ranging from highways, arterials, and collectors down to local streets and cul-de-sacs.  These categories are most appropriate for expanding sprawl suburbs with low-densities.  But this type of thinking came to dominate traffic engineering and was increasingly seen as the ideal for all situations — leading to the destruction of older urban neighborhoods in order to cram larger streets into the original small-block grid-layout.  Even a recent effort by the Congress of New Urbanism to come up with a more smart-growth friendly alternative set of categories ended up defining them by access and speed as much as surrounding context.  The new mantra of “context sensitive design” – about which the Massachusetts Department of Transportation was an early advocate – ends up primarily dealing with creating a “transportation facility that fits its physical setting” rather than social interaction. And the demand for “complete streets” – a concept emphasizing the need to include accommodations for “all users and all modes” – turns out in practice to usually mean fitting sidewalks and bike lanes into whatever space is left over after car needs are satisfied rather than truly “designing from the outside inwards” by prioritizing pedestrian and cyclist facilities before dealing with cars.


Unless you are willing to start tearing down buildings – stores and homes – street width is a given, and limited.  So the amount of space allowed for different uses at different times is a key issue.  And cars and trucks – moving, parking, dropping off or picking up people and things – take up a lot of space as well as creating noise, pollution, and safety hazards for people without a metal armament.

But space is not the only issue.  Speed is also critical.  As many European cities have shown, cars and people and push carts and bicycles can share a plaza or street so long as everyone is moving slowly.  Many European residential and downtown areas now strictly enforce 20 Km/Hr limits – about 18 miles per hour!   Many US cities, Chicago is one example, have large “speed bumps” in residential areas – and despite fears that these bumps (as well as “raised intersections”) will hinder emergency access the city hasn’t burned down since O’Leary’s cow kicked over the lantern.

There are tools within the traditional Traffic Engineers kit to deal with these issues.  The problem isn’t coming up with solutions; the problem is that our various Transportation Departments haven’t been told to use them.


Boston’s Transportation Department, as part of its Complete Streets planning process, has innovatively pushed ahead of traditional thinking by coming up with a set of alternative street categories including Downtown (Commercial, Mixed Use) and Neighborhood (Main Street, Connector, Residential) types as well as Boulevards, Parkways, Shared Streets, and Industrial Roads.  To a large degree, they are defining the categories by the types of activities that happen on and around the pavement.  For example, about Neighborhood Mainstreets the draft documents say, “Because these streets are a meeting ground for residents, they should be designed to support gathering and community events such as farmers’ markets, festivals, and local communi­ty events. In addition they are characterized by public facilities such as libraries, as well as community and health centers.”

The ultimate issue, of course, is how these definitions translate into road designs and then how the planned design actually gets implemented on the ground.  The push-back from people and interests unable to see anything beyond the uncertainty of changing what currently exists, or who profit from the car-centric status quo, will force compromises at every stage.  As we know from the Big Dig, there is a long stretch from idealistic concept to crumbling concrete.  There will be several opportunities for public input and comment as the Complete Street Guidelines are implemented in projects – it is vital that people in favor of this approach participate and speak up!

In the meantime, we need to continue to encourage creativity around this issue.  And in that spirit, here are some ideas about possible People-Activity-Based Street Design Categories. These are probably most relevant to urban areas, and obviously leave out many possible categories.  They may be applicable to some of the inner-ring and more developed suburbs.  In any case, they are simply meant to suggest an approach – and I welcome additional suggestions.

Densely Mixed Use — Think of Boston’s North End’s narrow and winding streets or even parts of Newbury Street: lots of people, so much traffic that it’s moving at a snail’s pace while people search for a parking spot.  What if these were treated as “shared space” – open plazas available during business hours and/or evenings to any person, non-commercial vehicle, or type of activity (within legal limits of noise, pollution, and other nuisances) in any part of the space – but with a speed limit of 5 mph.  Delivery trucks of more than mini-van size would be given priority from 5am to 9am, but otherwise forbidden.  Overnight residential parking would be allowed.  Garages for longer term parking and store employees would be on the “outside” of the block.

Residential – Think of those parts of Roslindale and Dorchester full of houses and smaller apartment buildings with a mix of families, elderly, and young people; car traffic is light and mostly composed of people arriving or leaving the neighborhood.  What if these were treated as “neighborways” – tree lined, with speed bumps, residential parking, bulb-out corners, and other traffic calming measures.  There would be no need for bike lanes or traffic lights – stop signs and raised intersections would control intersections.  The speed limit would be 20 mph.

Vulnerable People Areas – Think of schools and daycare centers, hospitals and health clinics, elderly housing and community centers, playgrounds and parks:  lots of slow-moving or distractible people running out from unexpected spots with parking mostly serving those people unable to walk or bike to those institutions and locations.  These would be treated as “special safety zones” with the full array of traffic calming features – 15 mph speed limit, speed bumps, curb extensions, wide zebra-marked pedestrian crossings in mid-block as well as at intersections, well-timed pedestrian signals, etc.  Garages for longer term parking and store employees would be on the “outside” of the block.

Boulevards and Parkways – Think of Commonwealth Avenue:  wide, tree lined winding streets with space for wide sidewalks and separated cycle tracks.

Commercial Districts – Think of Mass Avenue: lots of people coming and going for short-term stops; a place to switch modes, from bikes to subway, from car to train.  Where appropriate, streets would be one-way for cars but allow two-way pedestrian and bicycle traffic (with the “wrong way” bikes confined to a “contra-flow” lane on one side).

Throughways – These would be the connectors between areas; laid out as a Complete Street accessible to all modes but more evenly balancing priorities among transit, pedestrians, and bicycles than is typically done today.

Travel – Think of the Mass. Pike.  Eisenhower was right – there is a need to facilitate long-distance transportation of people and things between cities, and trains or buses don’t always fit the need.  But Eisenhower never envisioned that these monstrosities would extend into the cities, and neither should we.


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