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The reason we have as many wide roads as we do is peak hour congestion.  This congestion happens 2-3 times a weekday and 0-2 times on weekends, all over America.  The most common peaks are the AM and PM rush hours, when 20% of the miles traveled in America happen in 10% of the time.  If your city has congestions, congratulations, you are doing well.

Congestion is also the first bleat of  people in traffic.  It is galling to be in stop and go traffic with no option but to sit there like a jerk with your foot hovering over the gas pedal, waiting for your chance for 5 or 10 feet for progress.  Particularly when the car was sold to you with the promise of a very large team of horses.  Cars were made to go fast, not sit in traffic.  Changing lanes is useless, because everyone else sees the same opening you do.  By the time you’re in the other lane, the lane you were in is now clear of cars like you and darts ahead of the formerly clear lane you just occupied.


The peak hour is really a peak 15 minutes in most roadways.  Only a few  traffic light cycles at most.  Heck, the peak of peak is really just one cycle of a traffic light in most places.  I feel for the saps in this traffic, because they will be moving in this slow pitiful platoon along the entire  length of the arterial until they arrive at their destination.  If they fall back to get a Egg McMuffin, they drive in less stressful  traffic, but they will get where they are going later.  They are stuck in the plug of the worst traffic, that moves all over every metro from homes to works in the morning and back in the evening

Managing congestion is really about managing this plug.  Highways and parking are designed to accommodate this plug.

I live in the worst traffic metro in the United States, but I almost never feel it.  I live with 2 miles of my work and a metro station.  Though I would be healthier if I biked to work more often, I usually take my wife to the transit station, and then drive in to work from there.  A journey of about 5 miles.  If we get the timing wring (8:15 AM) we are within the plug, but we are back out of it in 3 blocks.

So how could we scale this idea.  I’m not suggesting everyone leave that close to their work, though Americans are making more choices like that to avoid traffic, just like me.  The story of America’s metros has been jobs moving out to the suburbs, and people making suburb-suburb commutes to avoid the trouble of the plug into town.  This just means there are plugs in more than one direction, of course.

Transit won’t work, because the plug is like a braid.  You have thousands of loose trips from all over with a thick braid of congestion in the middle, but the individual hairs of the braid, the trips, go all over the place once they get closer toe their destination.  Carpooling might help the plug, but it is hard to get people to agree on a time, origin and destination.  Only in the largest highways does carpooling really work.

What about dirverless cars?  Like a moving sidewalk for cars.  The dream of driverless cars offers much closer following than the two second reaction times of human drivers.  What if we just packed them in and drove them smoothly?  This would work in freeways, where most the turning movements are tangential lefts onto exits, but not on arterials.  Every traffic signal would be an opportunity to accelerate and decelerate, making driverless traffic only marginally better than it is now.

Stop lights are timed in equity to allow cross traffic a chance to cross the road or enter the arterial.  If many arterial drivers had their way, cross traffic would never get the opportunity of cross for the entire rush hour.  This would, of course, cause ruinous backups along the cross streets, so a compromise has to be mad.  Signals can be sensor actuated, so that they don’t have a set cycle but a orderly response to demands.  OIf a lot of cross left turns need to get onto the arterial, then the signal can throw them a left turn signal until it sees no more cars in the left turn lane.  An orderly yellow, then a red signal will precede the resumption of cross traffic in the other direction, or movement along the crowded arterial.

The plug is important, because it determines the sizing of our roads.

Most roads are too wide for their midday conditions.  Cars skate ludicrously free and fast on two or three lanes in their direction, with turn lanes offered and seldom used at every intersection.  Lanes cost an average of $3 Million  a mile to build and $9 thousand a year to maintain.  This is not costless.

If it rains, the road is designed to shed water, to stay dry, to keep friction for those wheels so that the cars don’t go knocking into each other and killing occupants..  Every mile of road is an acre and a half an acre of impervious surface.  That acre and a half usually drains straight closest stream.  In even a moderate rainfall, that acre and half flushes  about a hundred cubic yards of rain (now storm) water  to your local stream.  Imagine your living room.  Now fill it with water and move it at 10-15 MPH.  No wonder scour is the #1 source of sediment pollution in America.  And sediment is the #1` source of water pollution in America (cf. Ken Cuccinelli).

Walkers see this expanse of asphalt filled with fast cars and thing thrice before crossing it.  Bikers, driving on its margins, have to worry a lot more about a free flowing car moving at 45 MPH than one stopping and starting at 10 MPH.  If the pilots in traffic are tired, all the worse.  Killing a biker is a trivial matter of a sneeze, changing the station or drifting to the side of the road.  Not really a moving violation, just a moment’s inattention.  The plug is actually one of the best times for walkers and bikers, because no one is moving at a killing speed.  They are often distracted by the anguish of being in the plug, however, and entirely focused on the cars around them.

The plug offers more disadvantages than advantages.  I’d like to explore a  more elegant solution to getting commuters where they are going.


100 cars and 6 motorbikes. Probably in Japan unless we’re looking through a mirror. Note the pure blankness of the lanes in the opposite direction. This is a city with a strong downtown.