Phoenix Car Culture: Level-of-Service

Phoenix is a car city. Are you shocked yet? There are many reasons why Phoenicians utilize the personal automobile as their primary mode of transport. Many cite the heat but weather doesn’t stop cold winter cities like New York, Seattle, or Chicago from having low(er) car usage, so I don’t buy that argument. It’s more likely a combination of land use and transportation infrastructure. I was reading through the Downtown Phoenix Plan because that’s just what I do, and there were a few things that stood out to me that are worth noting. In Chapter 5, the Circulation and Parking Plan, page 5-4 explains what is expected of future traffic conditions. First, from the leading paragraph on that page:

“…The major congestion points will continue to be located along the access routes to the freeways and on the north-south arterials (7th Avenue and 7th Street).”

 Followed by the paragraph entitled “Future Traffic Conditions”:

“…Comparison of the estimated roadway capacity with the projected traffic volumes shows that existing congestion will likely increase with new areas of congestion developing. Roadways where congestion is likely to increase include 7th Street and 7th Avenue, Roosevelt and McDowell Streets. Roadways where existing capacity is expected to exceed projected future demand include 1st Street and 2nd Street between I-10 and Fillmore Street.”

There is clearly disconnect here between what is or isn’t an acceptable level of inconvenience for drivers. The planning document indicates there is an unacceptable level of congestion on the 7’s, Van Buren, and Roosevelt as-is, and further development will increase that congestion. A 2010 Level-of-Service (LOS) study conducted by the Maricopa Association of Governments (MAG) shows morning delay at 7th Avenue and Van Buren as “LOS-E”, 7th Avenue and both I-10 and Washington as “LOS-D”, and all other downtown intersections surveyed as “LOS-C” or better. The following chart shows the LOS thresholds in this survey:




Control Delay per vehicle (seconds per vehicle)




<= 5




> 5-15




> 15-25




> 25-40




> 40-60




> 60


 The evening peak hour shows a similar picture with the same LOS-C and LOS-E locations, but Central and Van Buren deteriorated from LOS-A to LOS-E. Of the eight intersections surveyed during peak periods, none received failing grades.

 The Federal Highway Administration (FHWA) references the Highway Capacity Manual defining LOS as “the additional travel time experienced by a driver, passenger, or pedestrian.” This includes time spent decelerating, in queue, and accelerating when compared to free flow traffic conditions. Now compare the MAG threshold with the FHWA’s Signalized Intersections Informational Guide.



Control Delay per vehicle (seconds per vehicle)




<= 10




> 10-20




> 20-35




> 35-55




> 55-80




> 80


It’s indicative of the culture that persists here in Phoenix that not only are our roads designed for high speed (50-60 MPH design speeds), high-volume (mostly 3-lane major arterials) travel, the amount of delay at which an intersection is considered inadequate is lower than the federal standards. The roadways that are designed for high-efficiency travel have not been effectively designed for safe or comfortable travel by any other mode than an automobile, relegating active mode users to the side streets and increased travel delay.

I’m often one to scoff when a one minute delay through a corridor is what compels DOT’s to spend hundreds of millions of dollars to add a new freeway traffic lane, it’s an obscene amount of money to spend to save people one minute per day. But being as I utilize a bike for my primary mode of transport, and largely being relegated to high-stop thoroughfares such as 1st Street or Fillmore, I can understand how being delayed 30 seconds per intersection can become frustrating over long distances because every person riding a bike does it every day if we choose to avoid high-volume arterials*.

There’s much consternation about whether congestion is a good thing or a bad thing. Some people argue some congestion is good like Emily Badger in this Atlantic Cities piece. Paul Grover of the London Telegraph is one of the many people who prefers to focus on the downside of congestion (and to be clear, London’s congestion delays drivers more than the threshold mentioned in Badger’s article), so which is it? I think Matthias Sweet hits the nail on the head in the Badger article when he says: “Sometimes the cost of alleviating congestion is higher than the cost of the congestion itself.” We don’t always have to have free flow traffic to have a thriving economy. Some congestion slows people driving, which makes walking safer and biking more appealing, which moves more people at a lower cost, which creates lively streets where people want to live and spend money, which boosts the economy. And when more people are walking and biking, more cars are taken off the road (which we know are later replaced by induced demand), but the capacity of the roadway has increased significantly by the measure of moving people.

While this is anything but scientifically conclusive, my point is simply that LOS is not an adequate way to engineer our roads. The 7’s, Washington, Van Buren, and Jefferson are all much, much too wide and fast to be a part of any downtown, let alone one working to become more accessible by foot and by bike. If we continue to maintain an LOS E or higher on every intersection, it’s likely to involve widening roads or creating new travel lanes, fewer stops for traffic (and similarly fewer places for people on foot or bike to cross those major streets), and we’ll be less inclined to make changes to move more people faster even if it’s at the expense of moving fewer cars slower. We can and should be expecting a greater return on our investment of public infrastructure, because the amount of congestion savings we’re getting from the money we’ve put in to our wide roads and extensive freeways isn’t worth the decay and desolation of our urban cores.

*And even when I do ride on arterials, the timing doesn’t suit bike speeds very well. I’ll commute both directions on Brown Road through Mesa and if I ride right about 20 MPH between Gilbert and Recker Roads I can hit every green light, but any <10 MPH deviation either faster or slower and I will hit every red light (what I mean is, if I go 30 between intersections I can make the next light, or if I go 10 between intersections I can catch every light, but going 22 or 18 – no dice!).

UPDATED: This article was originally published on November 1, 2013 and updated on November 6, 2013. I added two before the last paragraph because I really didn’t feel like I concluded my thought. Hopefully this makes a little more sense now.


One thought on “Phoenix Car Culture: Level-of-Service

  1. Pingback: Changing the Regional Transportation Plan | Phoenix Bike Blog

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