Traffic engineering - helpful or harmful to cities?

As part of my work, it has become increasingly common for Council's to ask for a "traffic report" as part of a Development Application. This is increasingly not only for large developments such as shopping centres, churches, large scale subdivisions etc. but also for smaller developments including minor change of uses to existing buildings. The number of reports being requested as exploded exponentially during my time working in this field.

Management of traffic and roads is a legitimate function for government. Council's are therefore often the subject of complaints as a result of traffic problems, including where they are the result of a particular development.

There can be a view that it is in the public interest to make traffic within a city flow as smoothly and as fast as possible and that this is the main function of roads.

Past articles on this blog have discussed Le Corbusier’s "Radiant City" (ie. The Tower in the Park) concept. The Swiss-French architect hated the narrow, crowded streets of Paris. His vision? Demolish everything and replace it with identical 60-story glass skyscrapers, spaced far apart on a flat, grid concrete plain.

• The Traffic Engineering Takeaway: Separate everything. Pedestrians go on elevated walkways. Cars go on high-speed expressways below the buildings. Roads are strictly hierarchical (Highways to Arterials to Local streets).

• The Pro: It is ruthlessly efficient for moving vehicles from Point A to Point B. No intersections, no pedestrians crossing, no shops spilling onto the sidewalk. Pure velocity.

The twin of the alternative "Garden City" movement tended to be large scale urban motorways, as suburban sprawl spaced urban development further and further apart and almost everyone needed a car to move around. In many locations, it evolved into the Radburn model, which fostered complete separation of vehicles and pedestrians in a low density format. You park your car at the edge, and you walk through a tunnel under the road to reach your front door via a park.

Both of the above concepts led to questionable outcomes.

Jane Jacobs, who wrote, "The Death and Life of Great American Cities" generally despised traffic engineering as a profession. She didn't just critique it; she viewed it as a pseudo-science that was actively destroying the very fabric of cities.

Traffic engineers, in Jacobs’ view, operated on a dangerously simplistic equation: Cars = Traffic = Congestion = Build more roads. To her, this was a circular, self-serving logic that treated cities like machines to be optimised, rather than living ecosystems to be nurtured.

She had three specific, brutal criticisms of the profession:

1. They mistook "movement" for "place": Jacobs famously argued that a city street has three functions, and traffic engineers only cared about one: moving cars. They completely ignored the other two—safety (pedestrians) and socialising (the "footpath ballet" of shopkeepers, children, and neighbours). By widening roads and synchronising lights for peak-hour flow, engineers turned vibrant Sydney high streets (think King Street Newtown or Parramatta Road) into sterile "car sewers" that killed local economies.

2. They used "scientific" data to justify moral failures: Jacobs pointed out that traffic engineers relied on "Level of Service" (LOS) ratings—grading intersections from A to F based on vehicle delay. To her, this was a technical disguise for a value judgement: Prioritising the commuter from the suburbs over the resident who lives there. She said they never measured the "level of service" for a child trying to cross the street to get to school, or an elderly person trying to catch a bus.

3. The "Induced Demand" fallacy: Decades before it became a viral TikTok urban-planning fact, Jacobs eviscerated the core tenet of traffic engineering: build more roads to ease congestion. She pointed out that building more roads simply invites more cars, which creates more congestion, which demands more roads. She called it "the ruthless juggernaut"—a profession that could never solve the problem it was tasked with, because its very existence depended on the problem getting worse.

What did she propose instead?

She didn't want to abolish traffic engineers; she wanted to demote them. She wanted them to be servants of the city, not its masters. She argued that traffic should be managed by "diversity, density, and fine-grained street networks."

• Make streets shorter (more intersections) so cars are forced to slow down.

• Mix land uses (shops, apartments, offices) so people don't have to drive everywhere.

• Narrow the roads and widen the footpaths to make walking pleasant.

  
  

In her world, a traffic engineer's job wasn't to measure the "peak-hour capacity" of a four-lane arterial; it was to figure out how to calm traffic so that a city could breathe.

It can be a problem where an entire city and it's roads are simply seen as a "thoroughfare" rather than a place in itself that is worth living in and spending time in. Congestion of cars is not always a problem and can sometimes be a sign that a city is actually working (so many people want to be in this place that they are willing to sit in traffic to get there). This is not to say that all traffic engineering is necessarily bad and that there aren't sometimes legitimate traffic problems to solve, although other fields of engineering have arguably made a far greater contribution to cities eg. developing reticulated water and sewage systems, building bridges and reducing flooding.