[sustran] Re: freeways solve traffic congestion - not?!

[Todd Litman]

At 09:32 AM 9/29/98 +1000, Bron wrote:
>>Transurban is spending millions promoting CityLink, including saying that
>>it will bring about lower emissions. I have a memory tickling at the back
>>of my brain that freeway builders in the US made that claim, and had to
>>discontinue it after someone challenged them. Do you know anything about
>>that?  Do you think any of your vast contacts would know of that case? Or
>>is purely my imagination?

Over the last few years a number of transportation planners and economists
have pointed out that highway investment studies that fail to consider the
effects of "generated traffic" (also called "induced travel") will
overstate the benefits and understate the full costs of capacity
expansition. This was treated as a theoretical issue until recently when a
number of studies showed that the amount of traffic generated can be
significant. In congested urban conditions, 60-90% of increased roadway
capacity can be filled within a few years by trips that would not have
otherwise been made. An additional important point is that these additional
trips consist of relatively low value vehicle travel that consumers
themselves are most willing to forego when congestion increases.

There is still considerable debate about this issue. The report "Expanding
Metropolitan Highways; Implications for Air Quality and Energy Use" by the
Transportation Research Board (1995) actually argued that the air quality
effects of generated traffic are uncertain (if you get the report be sure
to read Michael Replogle's brilliant rebuttle to the majority report), but
U.S. air quality laws are increasingly being used to prevent increased
highway capacity expansion in many cities that have significant air
pollution problems. 

I'll be glad to send a copy of our report "Generated Traffic: Implications
for Transport Planning" which discusses these issues in detail and provides
references of the technical studies on the amount of vehicle travel induced
by increased roadway capacity.

Sincerely,

Todd Litman, Director
Victoria Transport Policy Institute
"Efficiency - Equity - Clarity"
1250 Rudlin Street
Victoria, BC, V8V 3R7, Canada
Phone & Fax: 250-360-1560
E-mail:      litman at islandnet.com
Website:     www.islandnet.com/~litman