Stephen Rees's blog

I am quite sure that none of what I write on this blog is of any surprise to my regular readers. The purpose of this post is simply to host an important piece of research which clearly has had no impact whatever in this part of the world. Oddly enough I am now able to offer you the complete pdf version of the publication because it has been used to support the case of the removal of the Gardiner East expressway viaduct in Toronto.

The Vancouver Courier has an article by Mike Howell who cites Ian Adam to support the contention that somehow the removal of the viaducts east of downtown will be a disaster and somehow this inevitability has escaped the attention of those currently responsible for traffic management in the area.

Ian Adam, who retired in 2008 as the assistant city engineer of streets and structures, said he believes the loss of the viaducts will create more traffic congestion in Chinatown, Gastown and nearby areas.

“Anybody who thinks you can take down two major viaducts like that, which handles 60,000 people a day and a thousand heavy trucks a day — and not have some impact — they’ve got to be dreaming in Technicolor,” said Adam, who once held the position of what is now called director of transportation. “I would say leave them up. They’re a $100-million asset that’s doing a job.”

This is a common theme with the mainstream media. When the Vancouver Sun reporter Jeff Lee covered the recent SFU City Conversation on the Removal of the Viaducts he made a huge effort to chase down Marguerite Ford, a long retired NPA Councillor who has no faith in traffic engineers. She is convinced that they do not understand how traffic works and that things will get worse, although she says she is not against removing the viaducts.

Both Ian Adam and Marguerite Ford are unaware of the research done in many places where traffic lanes have been reduced, freeways closed, viaducts removed – all around the world – and somehow the traffic adapted. I got interested in this phenomenon when I lived in London and the venerable Albert Bridge had to be closed to vehicular traffic for safety reasons. The traffic simply adapted, congestion did not get worse, and life went on. Phil Goodwin was a colleague of mine at the GLC’s Department of Planning and Transportation and went on to a distinguished academic career. He was interested in how traffic models needed to be adapted to become more realistic. Because they have no way to forecast either induced traffic – trips that appear on the network because of additional capacity (a new freeway or a new bridge) – or disappearing traffic – trips that no longer are made when a network loses capacity.

Here is the abstract

Reallocating roadspace from general traffic, to improve conditions for pedestrians or cyclists or buses or on-street light rail or other high-occupancy vehicles, is often predicted to cause major traffic problems on neighbouring streets. This paper reports on two phases of research, resulting in the examination of over 70 case studies of roadspace reallocation from eleven countries, and the collation of opinions from over 200 transport professionals worldwide. The findings suggest that predictions of traffic problems are often unnecessarily alarmist, and that, given appropriate local circumstances, significant reductions in overall traffic levels can occur, with people making a far wider range of behavioural responses than has traditionally been assumed. Follow-up work has also highlighted the importance of managing how schemes are perceived by the public and reported in the media, with various lessons for avoiding problems. Finally, the findings highlight that well-designed schemes to reallocate roadspace can often contribute to a multiplicity of different policy aims and objectives.

The original citation is Cairns, S; Atkins, S; Goodwin, P; (2002) Disappearing traffic? The story so far. P I CIVIL ENG-MUNIC , 151 (1) 13 – 22.

Here is the full text as a pdf Disappearing traffic the story so far which you can download

Both Adams and Ford appear to believe that the number of trips on a network is absolute. That any change to the network must therefore accommodate all the trips currently being made – and, by extension, any forecast of future trip making. Typically, models used to predict travel have also fallen into the same trap – leading to the never ending cycle of predict and provide which has only ever produced more vehicle trips, and worse congestion. The gravity model treats motor vehicle trips as though they flow like water, and thus have to be accommodated to avoid flooding. In reality traffic behaves more like a gas that expands and contracts to fill the space available.

You also need to bear in mind that the engineers responsible have also observed that traffic into downtown Vancouver has been declining, and the network they are proposing can easily accommodate all of the current trips with some slight delay for cars entering the downtown during the morning peak from the east. Among the “behavioural responses” which will occur, once the viaducts have been removed are trips will be made at different times of day, trips will be combined  – so that more than one errand can be completed in the same journey – trips will divert to other equivalent destinations and some trips will switch modes. There will be a few people who decide to stop driving their single occupant vehicle and try the same trip by walking, cycling or using transit. Many trips in this city are short enough to be accomplished in this way, and most people who try the alternatives will prefer them to driving. This is already apparent here, as elsewhere. Though obviously 70 case studies across eleven countries were not enough to convince some. Though this stuff is also really old: March 2002 publication. There have been many places since then that have followed this advice and found that it worked. We will too. Actually, we have. Point Grey Road and the Burrard Bridge ought to be enough evidence – even if all those protected bike lanes downtown which seem to be working quite well too are not convincing either.