TDM – A World Streets Primer

TDM HOV lane

Since TDM (Transportation Demand Management) is a key pillar of the New Mobility Agenda strategy, and of our now forming-up Five Percent Challenge Climate Emergency program, it is important that the basic distinctions are clear for all.  In one of our recent master classes, when several students asked me to clarify for them, I turned the tables instead and asked them, since we are now firmly in the 21st century, to go home, spend a bit of time online and come up with something that answered their question to their satisfaction.  Here is what they came up with, taken whole hog from (which we then lightly edited together and offer for your reading pleasure).

Quick-start references:


Back in the 1960s, the unquestioned solution adopted to reduce traffic congestion was to build more roads to accommodate the increasing demand.  However after some years and as demand continued to grow, this engineering measure was rapidly found to be ineffective. So then in the 1970s, the concept of TSM or Transportation System Management  was introduced to look at ways to better manage the existing transport infrastructure. A decade later TDM or Transportation Demand Management was implemented in the early 1980s to serve the purpose of changing human behaviour to reduce traffic congestion.

The main difference between the two is that while TSM strategies focus on imposing (to some extend) physical changes to the infrastructure, TDM targets traveler behavior, mode choice and employers to lower traffic demands on the roads during peak travel times. That is to say that while drivers are obliged to conform to TSM measures, they have the choice of choosing whether or not they want to follow TDM measures. To an extent, the success of TDM measures is more dependent on individual motorist compared to success of TSM measures which rely more on the measures they implemented.

The similarity between TSM and TDM is that these two policies serve the same aim of reducing traffic congestion, without utilizing more lands to build more lanes and roads. Both these policies look at ways to maximize the efficiency of the existing infrastructure without the need for addition of new and costly system. Both TSM and TDM look into ways of providing a safer and more efficient transportation system for the public.

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Read on, via World Streets at

Congestion management measures - Australia Nov 2006 table
Source: Congestion Management Measures, Sydney, Australia

About the editor:

Eric Britton
13, rue Pasteur. Courbevoie 92400 France

Bio: Founding editor of World Streets (1988), Eric Britton is an American political scientist, teacher, occasional consultant, and sustainability activist who has observed, learned, taught and worked on missions and advisory assignments on all continents. In the autumn of 2019, he committed his remaining life work to the challenges of aggressively countering climate change and specifically greenhouse gas emissions emanating from the mobility sector. He is not worried about running out of work. Further background and updates: @ericbritton | | #fekbritton | | and | Contact: | +336 508 80787 (Also WhatApp) | Skype: newmobility.)

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