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Why are cities not planned such that evacuation routes are already commonly used routes in the morning peak? If you plan city that way, all roads will saturate

Why are cities not planned such that evacuation routes are already commonly used routes in the morning peak? If you plan city that way, all roads will saturate equally instead of all traffic stuffing on highways and arterials, in non-evacuation scenarios. EDIT: descendant merged

nordsieck 8y ago
> Why are cities not planned such that evacuation routes are already commonly used routes in the morning peak? No one wants to pay for that level of capacity.
- deleted 8y ago
  [deleted]
- dsfyu404ed 8y ago
  This. People would rather have "rush hour" be from 3-8pm rather than pay for enough spare capacity that peak demand only saturates the system from 5-6. If a four lane highway is saturated for 3hr you'd need twelve lanes to cut that time to 1hr. That's a lot of money.
  - closeparen 8y ago
    Sprawl simply grows until the ample capacity is tight again.
    - dsfyu404ed 8y ago
      This applies to all modes of transit. It is as true for rail networks as it is for cars.
  - Hextinium 8y ago
    This is compounded by the fact that you cannot in fact build more lanes to handle traffic. Supply just meets demand. https://www.wired.com/2014/06/wuwt-traffic-induced-demand/ https://www.wired.com/2014/06/wuwt-traffic-induced-demand/
jcranmer 8y ago
In normal use, the peak travel pattern is essentially a unidirectional peak into the city in the morning and the opposite direction in the afternoon. That usually calls for a load that can handle the peak unidirectional traffic with the other direction being fairly empty, as managing the reversibility of lanes is difficult. (That said, the highway near to me right now does have three lanes of HOV that reverse direction, although that is one of the longest stretches in the entire world of such reversibility that is regularly exercised). However, there is an important difference between the regular commute and evacuation in terms of traffic patterns. In the regular commute, the flow generally extends only between the suburbs and the city core; in an evacuation, you generally need to go a much further distance, well beyond the furthest suburbs. As a result, you're looking at carrying evacuation routes on roads that are only meant to handle at worst summer vacation inter-city travel, so you see 12 lanes of traffic have to scrunch into 2 lanes of traffic.
manigandham 8y ago
They're completely different scenarios. Commuting is usually one-directional towards the center of the city and business areas with the working population. Evacuation is outward to completely leave the city, and includes everyone and their luggage, while being squeezed through suburban areas to just a few interstate highways.
- anticensor 8y ago
  Yes, but planning to make sure commuting and evacuation patterns identical would make the city sufficiently distributed. You would obliterate the CBD problem which causes rushed congestion in roadways. You would just need to go further to evacuate such a city.

nordsieck 8y ago

> Why are cities not planned such that evacuation routes are already commonly used routes in the morning peak? No one wants to pay for that level of capacity.

deleted 8y ago
[deleted]
dsfyu404ed 8y ago
This. People would rather have "rush hour" be from 3-8pm rather than pay for enough spare capacity that peak demand only saturates the system from 5-6. If a four lane highway is saturated for 3hr you'd need twelve lanes to cut that time to 1hr. That's a lot of money.
- closeparen 8y ago
  Sprawl simply grows until the ample capacity is tight again.
  - dsfyu404ed 8y ago
    This applies to all modes of transit. It is as true for rail networks as it is for cars.
- Hextinium 8y ago
  This is compounded by the fact that you cannot in fact build more lanes to handle traffic. Supply just meets demand. https://www.wired.com/2014/06/wuwt-traffic-induced-demand/ https://www.wired.com/2014/06/wuwt-traffic-induced-demand/

jcranmer 8y ago

In normal use, the peak travel pattern is essentially a unidirectional peak into the city in the morning and the opposite direction in the afternoon. That usually calls for a load that can handle the peak unidirectional traffic with the other direction being fairly empty, as managing the reversibility of lanes is difficult. (That said, the highway near to me right now does have three lanes of HOV that reverse direction, although that is one of the longest stretches in the entire world of such reversibility that is regularly exercised). However, there is an important difference between the regular commute and evacuation in terms of traffic patterns. In the regular commute, the flow generally extends only between the suburbs and the city core; in an evacuation, you generally need to go a much further distance, well beyond the furthest suburbs. As a result, you're looking at carrying evacuation routes on roads that are only meant to handle at worst summer vacation inter-city travel, so you see 12 lanes of traffic have to scrunch into 2 lanes of traffic.

manigandham 8y ago

They're completely different scenarios. Commuting is usually one-directional towards the center of the city and business areas with the working population. Evacuation is outward to completely leave the city, and includes everyone and their luggage, while being squeezed through suburban areas to just a few interstate highways.

anticensor 8y ago
Yes, but planning to make sure commuting and evacuation patterns identical would make the city sufficiently distributed. You would obliterate the CBD problem which causes rushed congestion in roadways. You would just need to go further to evacuate such a city.