Tuesday, April 11, 2006

Highway one and triple convergence

I recently had a conversation with a friend (Nancy Callan, author and environmental food activist) about the expansion of highway one. I mentioned that freeway expansion rarely solves the congestion and often during peak hours congestion returns to previous levels in a matter of months. This occurs because of triple convergence (also here). At the time I had forgotten what the three convergences were but after a little research here they are:

  1. many drivers who formerly used alternative routes during peak hours switch to the improved expressway (spatial convergence);

  2. many drivers who formerly traveled just before or after the peak hours start traveling during those hours (time convergence);

  3. some commuters who used to take public transportation during peak hours now switch to driving, since it has become faster (modal convergence)

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