Congestion of traffic has a cost.

Even I, who sees and has argued that traffic congestion saves lives, can see this. The frustration of slogging down a long arterial in extra minutes of stop and go traffic waiting for one light to change after another is infuriating, and stressful.

Of course, congestion is not a linear thing. Traffic can be free flow at 1,000 vehicles per lane-hour, and gummed up by 1,100. My numbers may be off but the idea is consistent with reality. Congestion is a marginal phenomenon.

The main times for congestion are morning and afternoon weekdays and midday Saturday. Arterials all over the nation get gummed up at the same time, because we are making 20% of the trips in 10% of the clock. The congestion during these periods is why we size the roads the way we do. Engineers don’t get called on to redesign, and grants don’t get made from the general fund to widen roads that are not congested. Even though congestion does not happen on most roads, most of the time.

There’s a six lane highway 1 block from me with absolutely clear 45 mph traffic right now for this very reason.

Some of the people in congested are just going to get breakfast, or are commuting to jobs 2 mile away, or are shuttling kids to schools one mile away.

If people could safely and easily bike to breakfast, commute, or to school, those carts would not be in traffic. If 10% of the trips in traffic could be taken on bike, you would not have congestion. You would have a fuller bike lane, and a free flowing traffic arterial. The capacity of a bike lane around 1,800 bikes per hour, more than enough to absorb the congestive traffic margin of three arterial lanes.

So, if a bike lane network is functional enough to allow people to avoid traffic, cutting down on congestion (which has a cost), then is the bike lane network paying for itself? Unfortunately, very few places have a bike lane network good enough to find out, but I’ll run some numbers to see.

The cost of congestion as calculated by the Bureau of Transportation Statistics and the Texas Transportation is about  $21 an hour per driver.  
So, if the cost per driver of an hour of congestion is officially $21, how much traffic do we need to remove from a road to save that money?  In case $21 seems trivial, congestion costs over $1 billion to the average large metro, and over $4 billion for very large metros (> 3 million population).  This cost is not on any budget, but is distributed among millions of commuters every weekday of every year.

Anything that can be done to reduce this delay would save that much for each driver “convenienced” by the faster flow of traffic.  The difficulty that many meters have with this is that they don’t have any way of getting around except traffic.  Their transit systems are mired in traffic, stop often, and have headways over 15 minutes or even an hour between buses.  Their housing and employment are sorted into zones too far part to navigate by bike or on foot.  The transit they do have is best at connecting poor, low skilled neighborhoods with high-paying, huh skilled jobs.  The transit system and the neighborhoods would do better of they connected people to jobs they were likely candidates for.

Many cities have been built for the last 80 years with the idea that the only way to get around was in traffic.  Because that was indeed the prevailing notion.  Traffic, like any set of heavy and fast independently piloted vehicles, needs a lot of space for safe operation, and even more space if the drivers fancy that they want to leave in the same car they arrived in.  Parking is vital to the smooth operation of traffic, however, as cars parked in traffic lanes tend to make movement difficult for other cars trying to get somewhere.  

Finally, adding lanes to roadways does indued make the system run faster, but it does not make the highway run faster.  If a NIMBY (not in my backyard) advocate wants to fight something that will genuine depress their property values for perpetuity, they should oppose any attempt to widen (or “improve”) the road in front of their house.  Drivers ion the network rightly  see the wide new inviting road as lower cost pass to get where they are going.  The typical addition of 10% of road capacity is met with a 9% increase in traffic on a road, within the first year.  It does not take long for the road to become as congested as it was before There are many gravel roads in better neighborhoods maintained for the  very purpose of discouraging through traffic.  Through traffic serves communities little.  Even more through traffic serves this communities even less.


More on this later.