The Injustice of Peak Hour Myopia

Rush hour is a cruel tyrant. It grips our lives with grim and gritted teeth. Each morning and afternoon I feel it weighing my heart, as if the neighborhood air has filled with clouds of anger.

What can be done? Something must be done.

And we have tried. Our efforts have been legend, the scale of our striving is generational, historic, geologic. Lifetimes of strain against the force of this twice-daily choking, mountains of steel and concrete erected to cut through the rush hour knot.

But nothing seems to work. Rush hour lives on, and still we fight.


I took some pictures of “rush hour” so that you know what it looks like.

The Peak Hour focus: The Lexington and Randolph Example


The corner in question.

I’ve been lately thinking about how rush hour works in our decision-making. There’s an assumption that’s been bothering me around how traffic engineers and highway planners make decisions: the focus on “peak hour” traffic flow.

Here’s an example from Saint Paul, of a debate over a street reconstruction at an intersection — Lexington Parkway and Randolph Avenue — that’s right by a major urban freeway (35E) and a grocery store (Trader Joe’s). Because of the popularity of cheap cheese, rush hour traffic has been getting worse at the corner for a few years  (or so I am told). As the street is being reconstructed, the County did a study that recommended adding a turn lane, which would address rush-hour “level of service” (LOS) in two ways: decreasing “stacking” by adding the storage capacity of an extra lane, and by allowing cars to more easily turn on red around the corner.


Some of the options for street widening.

By making this change, the Ramsey County study projects that the average car will save a few seconds of time stuck in traffic. For example, according to the model the proposed layout would subtract 20 seconds of delay for Northbound cars while adding a 5 seconds to Southbound cars.

(Forget about future 2035 projections for now. Those represent a whole different assumption problem.)

randolph-lex-before-and-afterThe key thing, though, is that these time savings only occur during the peak hour. For the rest of the day, when the “capacity constraint” isn’t constraining much of anything, the impact on drivers would be negligible.

Meanwhile, for the entire day, the intersection would have worse “LOS” for everyone else, especially people on foot trying to cross the street. Adding a turn lane, widening the street, or adding a thru lane (which are three of the options) would increase speeds at the intersection at all times of the day and night, eroding safety for neighbors and anyone on foot.

And that’s the temporality of the trade-off when we focus on peak hours as the measure of our streets.


Typical traffic curve from NACTO.

The needs of the commuter vs. the needs of the neighborhood


A building on the corner.

Here’s a weird thought experiment that I had in my head. It might seem like common sense to weigh the effectiveness of a street (the “level of service”) by its worst performing times of day. But there’s a way in which this kind of thinking is inherently unfair to the people living along these streets.

Here’s what I mean: If you combine the two “peak hours” (giving them 2-hour time slots), you end up with 4 hours of the 24-hour day. That leaves 20-hours of the day that are “off peak”, times when the road will be “overbuilt” for the amount of traffic that it has.

Basically, transportation planners are always faced with a choice here: Do you give design priority to the people using the street for those 4 hours of the day at the expense of the people that “use” the street for the other 20 hours? 

engineer explaining things

The back of the napkin.

Using back-of-the-napkin type math, you can almost weigh the difference here.

Let’s say that existing ADT (average daily traffic) is about 15,000 cars per day. I can’t find this separated out by hour, but using another street (let’s say University Avenue) as a guide, I count that peak traffic per hour is about 400 cars per hour. (University Avenue, according to a recent all-day count, has 18,000 cars per day on average, and 320 AM peak volume and 400 PM peak volume on weekdays.)

So if you average that out to 340 cars per hour multiplied by 4 peak hours, you get 1,360 car drivers whose lives are improved by a varying number of seconds each by a new turn lane.

Let’s give that a “life improved” factor (LIF) of 1,360.

(Yes, I know this is absurd.)

Against that, you’re weighing the effect of widening a street, and marginally decreasing safety (through faster turns, increased speeds) all day for everyone who lives nearby. Whether that matters depends on a few things: How many people use the sidewalks? How many homes would be impacted? How many hours are we talking about?

Let’s guess. Right around this corner there are about ten homes, a small two-story apartment building, and one large apartment complex (the Lexington Park Apartments, which has 64 units).

Saint Paul’s average household size is 2.5 people, but let’s round down to 2 because of the apartments. That leaves you with about 160 people in close proximity to the corner who’s everyday environments will be negatively impacted by widening the street, people who depend on either the corner here, getting across the street safely, and/or play in their front yards in very close proximity to these two streets.



Here’s the magic of the math. Because the street is getting widened and speeds are increasing 24 hours a day, the temporality is magnified. While you only count each car’s trip once, each neighbor’s experience is accumulated through the day. How many times a day does the average person leave the house? How many times a day does the average person walk across the street? How many times a day does the average kid play in the yard (or want to play in the yard, only to be told “it’s too dangerous”)?

Whatever that number is, that’s the number by which you multiply the “life improved” factor (LIF). 160 people [multiplied by] their changed experience of the street during a full 24-hour day.

So we’re talking about LIF anywhere from 320 (people go outside / notice the street twice a day)  to 1,600 (ten times / day) or more.

Obviously this is all bullshit. There are all kinds of of data problems with this, most noticeably that traffic aggravation, noise, safety concerns, and seconds of saved time are not commensurable things. And the non-car data is really bad. We have firm, exact counts of cars and their stopped seconds, but nobody counts pedestrians. Nobody carefully surveys nearby neighbors about how traffic speeds affect their everyday lives. We don’t really know how many people are using the streets or sidewalks on foot, bike, or experiencing the street from their front yards or porches.

Plus, I’m probably drastically undercounting the total population here. In Mac-Groveland, only 70% of people use a car to get to work. That’s potentially a lot of people who might move through this intersection on foot, bike, or bus. Similarly, Trader Joe’s is a magnet for pedestrian traffic. There’s also a bus stop that’s an intersection of two bus lines. There’s firm data for this (daily bus use at these stops), but I’m too dumb to access it. Suffice it to say that we could easily add a few hundred daily people, and potentially thousands of “points”, to that LIF total.

The basic trade-off is that focusing myopically on the peak hours means that a few seconds of the day of traffic for a commuter (once per day) are valued more than the all-day, every-day quality of life for the people living or walking in the neighborhood.


Another diagram from NACTO

Induced Demand and rush hour

supply demand curveThere’s another wrinkle to this problem, the sticky wicket of “induced demand.” The basic premise is that demand for fast automobile travel is not constant but variable, depending on things like the price of travel in both money and time (and probably things like comfort, attentiveness, etc). And congestion (the “supply” part of the curve) plays a big role in these decisions, acting as a key driver of driving decisions.

In other words, if traffic sucks at rush hour, you try to avoid it. If you have to go to the grocery store, the library, or the post office, you’ll probably choose a time when the roads aren’t clogged.   Or you might plan trips to and from work to “beat the rush,” arriving early or late simply because of traffic congestion.

What this means is that, even if you improve rush hour LOS, more people might simply take more trips during that time. After all, few people go “early” to work because they want to; most do so because of the influence of traffic.’

Thinking bigger about our streets

94-freeway-at-duskThe point of all this is that we get what we measure. The seemingly neutral LOS charts in an engineering study are actually a highly reductive view of the world, epistemological blinders that pay attention only to cars traveling at certain times of day. Like any science, a traffic study is making assumptions about what’s valued and what counts, and for generations we’ve acted under the assumption that rush hour is the most important time of day. And that leaves a lot of other factors out of the picture.

There are two simple solutions to the “peak hour” problem. One would be to move towards a “multi-modal LOS” that balanced LOS for cars against LOS for other modes of mobility. (Read all about that here.)

The other solution, a more temporal fix, is to simply expand and average the times of day where we measure congestion. In their Urban Street Design Guide, the engineers at NACTO write,

“Street design should be sensitive to how streets operate across all hours of the day, for all users. While understanding peak periods of intensity is valuable, the design of a street or analysis of a corridor should always seek to balance needs and functions of different time periods.”

They recommend collecting “multi-modal data” over “4-hour volumes (AM peak, midday, PM peak, and Saturday) to analyze typical traffic levels [and] average[ing] these 4 hours and use that volume to guide the design of streets and intersections.”

Street design is always a series of trade-offs. Automotive traffic flow comes at the expense of other things like pedestrian or automotive safety, quality of life for neighbors, access for other modes, etc. Improving one of these factors almost always involves a step backwards for one of the others. And that’s why the design hour mentality is inherently unfair. If you look at congestion in the big picture, and not just at the worst moments, a corner like Lexington and Randolph looks just fine. 

Don’t get me wrong. I hate rush hour as much as the next guy, if not more. It really sucks. But there’s not much we can do about rush hour anyway, and we shouldn’t let it dictate our lives or our streets.

Bonus: But if we don’t widen the street, drivers will get upset and break the law, won’t they?


29 thoughts on “The Injustice of Peak Hour Myopia

  1. Monica Millsap RasmussenMonica Rasmussen

    One thought I have is that through my outings, I’ve observed that some streets that have large rush hour auto traffic also have larger pedestrian traffic at the same time. People walking to parking ramps are pedestrians first. People walking to and from transit stops are pedestrians. As a pedestrian, it is not a joy to try to cross cars that are stopped or moving slow because of back ups. One never knows when a driver is going to see an opening that he or she will just try to make to get out of the way or to move past the intersection before getting stalled some more. I’ve also found drivers a lot more likely to stop for me at an intersection when traffic has been flowing than when they are barely moving during rush hour.

    I disagree that street design has to be a trade-off of better service for one group over the other. We’ve read about and experienced first hand better designs elsewhere in the country and in the world, designs that seem to accommodate multi-modal transit with very little trade-off in comfort and safety of all groups. We just have to be willing to accommodate the space required and to be serious in our concerns of the safety for all.

    1. Adam MillerAdam Miller

      Huh. On a bike, I feel exactly the opposite. Drivers already going slow in rush hour traffic downtown don’t seem to mind if they get stuck behind me for a block or so where the bike lane is closed. And crossing on foot in front of a stopped driver who knows there is no where to go feels a lot safer than being around free-moving cars that can’t be bothered to stop before turning right, for example.

      1. Monica Millsap RasmussenMonica Rasmussen

        Adam, it’s a weird concept, I know. One would think it would feel safer to be among slow and stopped cars, but I prefer the drivers and their cars would get away from me as fast as possible so that I can just be along my merry way and not have to think about them. When they are all around me, I feel like they are going to make sudden moves and not see me.

    2. Bill LindekeBill Lindeke

      Well, the “trade-off” I mean is that traffic volume for cars almost always comes at the expense of “level of service” for others. Almost all the things that guarantee free-flowing high-speed traffic (dedicated turn lanes, more lanes, wider lanes, signal priority) make the street worse for anyone not in a car.

      Maybe there are a few things that don’t fall into that category (e.g. reducing access points)? Not sure, but the majority of these variables do come at the expense of walkability (for example).

      1. Wayne

        We need to ban turns on red for pedestrian safety, and no amount of complaining by drivers will ever convince me their time is worth more than my life and limb.

        Whenever people are expecting to make a turn, both at stop signs and red lights, they never actually stop behind the limit line. I see maybe 1 in 10 (that’s probably generous) actually come to a complete stop in a way that doesn’t block the crosswalk. Just because they don’t see a pedestrian in the immediate area ready to cross doesn’t make it ok to pull right on up, because there’s a good chance they won’t be paying proper attention at some point and getting in that habit is extremely dangerous.

        There’s also the ‘uncorkig the bottle’ or ‘breaking the seal’ thing that happens with red lights where once the first person makes their turn on red, everyone behind them assumes it’s safe to go and doesn’t bother coming to a stop at the light to check for themselves. It just becomes a sad little slow-down pretend stop but most of the time they’re not even looking anymore.

  2. Matt SteeleMatt Steele

    Why even bother with the math when the idea of building a street’s automobile capacity for a tiny fraction of the day is so preposterous to begin with?

    As Chuck Marohn says, “Imagine if airlines operated seat capacity based on their peak demand days, the day after Thanksgiving or the day after Christmas?” His point is how much money they’d lose (and, by extension, how much money we chase adding roadway capacity used for momentary peaks). But there are real human costs too.

    1. Wayne

      Not to mention the growth predictions for vehicle traffic always wildly overestimate reality, yet they continue being used with little-to-no tweaks to the methodology. It’s a fantasyland that traffic engineers live in and the numbers are almost all bunk or meaningless in the context of actual reality that we live in. I’m all for trying to measure and understand the world, but they’ve ruined our cities by focusing on a terribly narrow aspect of it and not even doing a good job with that.

    2. Monte Castleman

      I’d accept your analogy if roads only met peak capacity twice a year too, instead of twice a day.

      What about if we built our electricity grid to average capacity instead of peak, and just accepted that brownouts and blackouts are just part of life and that nothing could or should be done; that people should just make lifestyle choices to use less electricity, or use electricity at different times, or there’s always candles rather than electricity. And powerlines are eyesores in the city and consume a lot of land that could be developed.

      1. Joseph TottenJoseph Totten

        So it uses a complete day to reach peak capacity for airlines, so it’s similar to planning for the daily peak-of-the-peak, or the 15 minute segment of the day which has maximum demand, (approximately 100 15-minute segments in a day, so 5/644 vs 2/365, comes out pretty similar). But we DO plan using the peak-of-the-peak we use this for queuing analysis, and ensuring the system doesn’t breakdown at those times, a.k.a. LOS is kinda ignored, but you have to ensure that your signal won’t cause problems elsewhere during that time frame. So we should ignore this?

        In addition, 1 – Private Utilities provide electricity, and often yes, you do see extreme loads creating brownouts, but we don’t see Xcel saying, “add more plants no matter what!” we see instead small increases in capacity and subsidies to homes which allow AC or appliances to be stopped during peak demand, we see other measures for reducing demand. 2 – To make your point you want to use the water system, government owned and operated and ever NOT delivering water to a customer is seen as a failure.

      2. Alex CecchiniAlex Cecchini

        Huh, it’s almost like there’s some sort of pricing mechanism built in to electricity rates at different times of the day to smooth user demand out, lower it at peak times, buy more efficient appliances, make homes/businesses more efficient, etc. And that we have different electricity generation means to handle baseload vs peaking loads. And a portion of utility revenue goes toward programs that help low-income people/businesses/public entities reduce their consumption (via efficiency, smart thermometers, insulation, etc). I wonder how those principles could be applied to a transportation network?

      3. Rosa

        I’m pretty sure Excel has the program where you get a discount if you let them limit your electricity during peak summer hours – we don’t have AC so we don’t qualify, but I’m pretty sure it’s on their menu. I grew up in a house on this plan, it just meant we couldn’t use the dishwasher or AC for a few hours on the hottest afternoon.

        Peak demand is partly engineered. If you design streets for less capacity, fewer people drive on them. If you have congestion pricing people plan around it. If traffic backs up, more people walk or bus or bike.

  3. Joseph TottenJoseph Totten

    Fall 2013 data from Metro Transit has ~90 riders per weekday boarding and alighting. (1 – 74 only, 83 was added in 2014. 2 – Because it’s both boardings and alightings no more math is needed for the total number of pedestrian trips. 3 – I should probably download the 2014 dataset.)

  4. David MarkleDavid Markle

    Obviously, making mass transit feasible and attractive to commuters would help: missed doing that with the 19th Century Green Line design. Horrible as rush hour in Chicago may be, imagine it without the El!

      1. Wayne

        Grade separation would have still been preferrable. It would have prevented the 3 pedestrian deaths so far on the green line this year. Just because the green line is a good routing doesn’t mean grade separation in the same route wouldn’t be an improvement. I know David has advocated for it being on 94, which I don’t agree with, but I do wholeheartedly think that running rail transit with a bunch of grade crossings is an awful idea.

        1. Adam MillerAdam Miller

          I’m all for grade separation and I see the appeal of a train along 94.

          I don’t agree that it’s the first (or second) line that should be built, that not building it there has hurt ridership (see, numbers), that “few” people commute on it (see, riders), that reducing commuter traffic should or could be a primary goal (see, induced demand), that not building it demonstrates a failure of process or that it’s an inherently flawed outcome to build LRT there with plans to extend the service to the suburbs.

          In a perfect world, we’d already have both a network of streetcars and a backbone of commuter rail. But that world is so far from the political reality that it’s a bit annoying when people make up their own facts to continue to complain that compromises were made in the name of actually achieving something.

    1. Joseph TottenJoseph Totten

      … I agree, but the north side Red Line has more than double the ridership of the south side. The south side is faster and runs in a freeway, the northside stops every other block (sometimes more). So if anything, we should have had MORE Green Line stops using your argument.

  5. David MarkleDavid Markle

    Which is why few commute long distances on it and why it does little to alleviate rush hour traffic. (It=Green Line)

  6. Will

    I ride the 74 sometimes. One time, we had to wait at a red light at Lexington. I can’t imagine the horror that those brave souls in their cars face. It’s also cruel fate that they’d have to slow down to 30 miles per hour after being on 35E, so, after the street is widened, they really should up the speed limit to 45. Now, everybody is happy! Right?

    It’s about time we introduce the suburban good life into the heart of the city.

    Snark. So much snark. I think we can all get by with a slight delay.

    1. Mike SonnMike Sonn

      I ride the 74 sometimes too. I start tensing up around Edgcumbe going east or Rooster’s going west in anticipation of the intersection. My blood pressure spikes! WHAT IF WE HAVE TO STOP AND WAIT FOR A LIGHT CYCLE?!

      Then we pass through unscathed and I let out a deep sigh of relief and begin fearing the next day’s commute.

    2. Wayne

      Don’t worry, we already build traffic lanes to highway standards in Minneapolis, so most people drive like that anyway since there’s next to no enforcement of traffic laws over here. Who’s the suburb now, St Paul? Ha-Ha!

  7. Alex SchieferdeckerAlex Schieferdecker

    The sooner we stop thinking about street design as a purely engineering problem and start thinking about it as a mostly economic problem, the better off we’ll be!

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  10. Toler

    Fantastic article.

    I appreciated being able to extrapolate your concept to the boondoggle that is the proposal to widen Highway 1 here in Santa Cruz County, CA.

    CALTRANS, certain interests and crony politicians are all for spending a billion dollars (let’s say conservatively, $600 mil for construction and at least half that for planning/development) on a 9-mile lane of asphalt between two urban areas of the county straddling beautiful coast, redwoods, and people’s neighborhoods, all to privilege car commuters over all others. Increasing GHG emissions and inducing demand, turning our beautiful county into a larger and larger parking lot. Meanwhile an old logging railroad lies roughly parallel, vacant and fought over by those who favor a light rail vs a bike trail.

    Please read the EIR document comment on the folly of widening Highway 1: Comments are being requested by the public until January 18, 2016:

  11. Jeff Barton

    It’s an interesting idea, worth teasing out further in concept. As for the specifics, I think you need to check your math here. The average of 320 and 400 (a.m. and p.m. peaks) is not 340. And, sadly, in most places, “rush hour” is no longer confined to an hour in the morning and an hour in the afternoon. It’s more like 2-3 hours on each side. So to be fair, you can’t assume that peak planning only benefits two hours per day. More likely, it benefits 4 or 5, or possibly 6 or 7 hours a day(depending on lunch traffic in this area).

    I suspect there’s also something going on with the peak volumes you’re using as the basis of your thought discussion. If the nearby University Avenue that you use as a model is seeing 18,000 ADT, as your report, then I don’t see how peak hour volume can be only 320 (a.m.) and 400 (p.m.). Just dividing 18,000 vehicles per day by 24 hours tells us the “average” hourly traffic (if there were such as thing) would be 750 — in other words, a number higher than you’re reporting as the peak. More likely a road with 18,000 VDT would have a peak hour count in the thousands. At a minimum, there may be confusion here between one-way and two-way traffic counts. In any event, we’re talking about pretty substantial changes in your numbers and the “life improved” index.

    Don’t get me wrong. I think it’s worth challenging the controlling philosophy of always designing for peak vehicle demand. Your point about the character of the street, and valuing the needs of other users deserves serious consideration. But within that context we need to accurately value the worth of traditional traffic improvements and how many drivers are affected.

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