AAA’s negative Thanksgiving traffic outlook a lot of common sense and normal conditions

Over a week ago, predictions by AAA about record Thanksgiving driving traffic started circulating. However, the reports did not add much useful information. Here is how the Chicago Tribune summarized it:

In fact, Chicago is expected to log one of the worst traffic jams of any big city during the Thanksgiving holiday season on Tuesday afternoon, according to an analysis by AAA and global transportation analytics company INRIX. Motorists should beware that the worst time will be between 5 p.m. and 6 p.m. Tuesday, when holiday travelers are expected to join post-work commuters on Chicago-area interstates. Already long travel times could quadruple, according to AAA…

In Chicago, area interstates may not only see one of the worst traffic jams over the holidays, the city also may come in second place for longest commute times to a major airport, analysts predict. The absolute worst time to take the Kennedy Expressway between downtown and O’Hare International Airport is 4:30 p.m. to 5:30 p.m Tuesday, when it could take an hour and 14 minutes, the analysis shows. Only a trip to New York’s Kennedy International Airport — the same day and around the same time of day — is longer at nearly two hours.

And from aaa.com:

Based on historical and recent travel trends for the holiday week, INRIX, in collaboration with AAA, predicts drivers will experience the greatest amount of congestion during the early evening – as early as Tuesday of Thanksgiving week – as commuters mix with holiday travelers. At its peak, drivers on Chicago’s interstates, for example, could see a delay of nearly 300 percent over the optimal trip.

“Thanksgiving has historically been one of the busiest holidays for road trips, and this year we could see record-level travel delays,” says Bob Pishue, transportation analyst at INRIX. “Knowing when and where congestion will build can help drivers avoid the stress of sitting in traffic.”

Two quick thoughts regarding this data. First, traveling during rush hour is a bad idea in any major American city. There are simply too many vehicles on the highways at these times and the traffic flows everywhere these days, not just into the city in the morning and out in the evening. Whether planning relatively short or long drives, it is necessary to plan to avoid rush hour.

Second, saying that the delay in Chicago could be “nearly 300 percent over the optimal trip” or the trip from downtown to O’Hare will take slightly over an hour is really not that abnormal. Perhaps the key is the comparison to the “optimal trip” which in metropolitan areas tends to be somewhere between 8 PM and 6 AM when truck and car travel is limited. I have this optimal trip in mind all the time when I make a drive to the local airports: without traffic, the trip takes this amount of time but adjustments need to be made for any daytime or early evening hours. In the Chicago area, all it takes is a little rain or snow or an accident and the Thanksgiving travel times predicted here are fairly normal occurrences.

All that said, this is good PR for AAA. Americans may like driving but they do not like traffic.

The roundabout capital of the United States is…

As Chicago area drivers disagree about existing and proposed roundabouts, the roundabout capital of the US is revealed:

Booster Dan McFeely of Carmel, Indiana, wants Illinois to embrace roundabouts.

“We have built 102 roundabouts to date, the most of any city in America,” said McFeely, Carmel’s economic development director. ” … We have steadily added them to Carmel over the past 20 years. They work wonderfully. And yes, we’ve seen a steady decline in accidents with injury.”

Carmel is regularly ranked as one of the best places to live in America. (It just took the #1 spot in Niche.com’s 2017 rankings. It also has done well in Money‘s rankings, taking the top spot in 2012.) Who knew the secret to their success was roundabouts?

As long as there are enough lanes and not so much traffic that people can easily enter the roundabout, I’m all for them. As a driver, I find little worse than traffic lights on timers where you sit for a long period of time with no cross traffic.

One interesting aside from seeing a suburban debate over a roundabout in recent years: they can take up a good amount of room compared to a traditional intersection. Therefore, they might be difficult to implement in older locations or where buildings are relatively close to the road.

Is the Naperville diamond interchange working?

The relatively rare concept of a diamond interchange opened at the Naperville intersection of I-88 and Route 59 in September 2015. Was the effort to reconstruct the interchange worth it?

The short answer: there has not been an official pronouncement. Proponents suggested the design has several advantages: fewer accidents since drivers are not making left turns onto or off of highway ramps, improved efficiency since cars can merge onto ramps on red lights, and less space needed. Here some pieces of evidence regarding the matter:

The Illinois Tollway is constructing another diamond interchange at I-90 and Elmhurst Road. Would they do this if their first attempt was unsuccessful?

Crashes at the intersection were down between 2015 (73) and 2016 (53).

-Since it is a busy intersection – over 180,000 vehicles a day – wouldn’t drivers and officials gone public if there were major issues with the new design? Some drivers still thought it odd as of April 2016 but Naperville issues said they were pleased.

According to DivergingDiamond.com, there are a number of diamond interchanges in the planning or construction stages across the United States.

The evidence seems to suggest the diamond interchange in Naperville is working. It still may be worthwhile to see when officials are willing to take credit or take a victory lap for their decision.

 

Zoning trade-off: privacy vs. adverse effects

The conclusion of Sonia Hirt’s book Zoned in the USA sums up the advantages and disadvantages of a zoning system that privileges the single-family home:

Arguably, zoning – the kind of zoning that makes explicitly private space the formative compositional element of America’s settlements – does deliver the gift of privacy to American families. But put all the other arguments mentioned in the previous paragraphs together, and one begins to wonder whether the original promises of zoning were either highly suspect from the beginning or have since been turned on their heads. Paradoxically (from the viewpoint of zoning’s founders), we may not have more pollution and worse public health with our current zoning that we would have if we had modified our land-use laws more substantially over the last hundred years.

As Hirt discusses, residents can have their own private homes – the largest new single-family homes in the world – but that comes at a cost of traffic and commuting, worse pollution and using more land, and worse health as well as some unrealized dreams of zoning including reduced crime. Some would argue that the privacy is overrated as well: compared to many other countries, Americans have given up on public life.

While it is easier to imagine mixed uses in dense urban neighborhoods – imagine Jane Jacobs’ vision of a bustling mixed use New York neighborhood – it is harder to imagine mixed use or zoning throughout the vast expanses of American suburbs. Even New Urbanists have tended to design neighborhoods or shopping centers dropped into suburban settings rather than the whole fabric of suburban communities. From the beginning of American suburbs, there was the idea that the urban dweller was escaping to a cottage in nature. The home out there offered refuge from people, dirt, and bustle. Today, this legacy lives on when suburban residents oppose certain land uses near their homes for fear of a lower quality of life and subsequently reduced property values.

Ultimately, would the American suburbs even exist without the fundamental desire for privacy?

Atlanta bridge collapses, traffic isn’t that bad

Urban highways are often very busy but when they are completely out of commission, it doesn’t necessarily lead to horrific traffic:

You’ll forgive our excessively clinical attitude about this damage—and it’s going to cost tens of millions to fix—but what we have here is a classic “natural experiment” of the kind economists and students of public policy relish. So what happens when we take a major urban freeway out of service for a couple of months? Are Atlanta commuters in for hours of gridlock every day and grisly commutes? Will the region’s economy grind to a halt as a result? We’ll be watching over the next several months to see.

So far, the results are consistent with what we’ve seen in Los Angeles and Minneapolis. Monday morning came, and something funny happened: traffic wasn’t so bad

So what’s going on here? Arguably, our mental model of traffic is just wrong. We tend to think of traffic volumes, and trip-making generally as inexorable forces of nature. The diurnal flow of 250,000 vehicles a day on an urban freeway like I-85 is just as regular and predictable as the tides. What this misses is that there’s a deep behavioral basis to travel. Human beings will shift their behavior in response to changing circumstances. If road capacity is impaired, many people can decide not to travel, change when they travel, change where they travel, or even change their mode of travel. The fact that Carmageddon almost never comes is powerful evidence of induced demand: people travel on roadways because the capacity is available for their trips, and when the capacity goes away, so does much of the trip making.

If Atlanta can survive for a month or two without a major chunk of its freeway, that’s a powerful indication that more modest steps to alter road capacity don’t really mean the end of the world. If we recognize that traffic will tend to adjust to available capacity, we then end up taking a different view of how to balance transportation against other objectives. For example, this ought to be a signal that road diets, which have been shown to greatly improve safety and encourage walking and cycling, don’t have anything approaching the kinds of adverse effects on travel that highway engineers usually predict.

I do think that this suggests drivers will adjust their behaviors based on what roads are available. At the same time, there is probably a tipping point where reducing too much traffic capacity would make a big difference. This might be especially true in car-driven places like Atlanta and Los Angeles that are known for sprawl. Presumably, places where traffic capacity could be picked up by other transportation options (such as closing the Embarcadero Freeway in San Francisco where driving is already a hassle and other options include BART, Muni, etc.) would fare better. Or, perhaps road capacity has to be reduced gradually so that people have time to adjust and make new choices about travel and where they live and work.

See earlier posts about what happened with Carmageddon I and Carmageddon II in Los Angeles

Better software to reduce traffic

Adaptive traffic software has helped reduce congestion in Ann Arbor:

Ann Arbor’s adaptive traffic signal control system has been playing god for more than a decade, but fiddling engineers continue to tweak its inputs and algorithms. Now it reduces weekday travel times on affected corridors by 12 percent, and weekend travel time by 21 percent. A trip along one busy corridor that took under three minutes just 15 percent of the time in 2005 now comes in under that mark 70 percent of the time. That’s enough to convince Ann Arbor’s traffic engineers, who just announced they’ll extend this system to all its downtown traffic lights and its most trafficked corridors.

To combat congestion, each hopped-up signal uses pavement-embedded sensors or cameras to spot cars waiting at red lights. The signals send that information via fiber network to the Big Computer back at traffic management base, which compiles the data.

This stuff works on a macro and micro level: If there are four cars lined up to go one way through an intersection, and zero cars lined up to move perpendicular to them, the light might turn green for the four. But a network of connected lights—like in Ann Arbor—will analyze the entire grid, and figure out who to prioritize to get the most people to their destinations the fastest. Advanced traffic control systems can even predict delays and congestion build-up before they happen, based on the ebb and flow of commutes…

The system knows when to lay off the change. “People kind of freak out if the signal is really different from yesterday or different from what it was five years ago,” says Richard Wallace, who directs the Center for Automotive Research’s transportation systems analysis group. For the most part, the system looks to tweak light patterns, not reshape the whole shebang from one hour to the next.

As we wait for the complete takeover by driverless cars, this could help ease our troubles. Small but consistent improvements like this could make a big difference to many commuters. Of course, it could also have the effect of encouraging more drivers who see that the commute is not so bad. Perhaps this is why the lights should be somewhat haphazard; it might unnerve a few of those drivers.

I assume there are some costs associated with putting in sensors and cameras as well as in developing the software and having employees to set up and run the system. How do these costs compare to the money saved in shorter driving trips? Or, what if this money had been put into opportunities like mass transit that would remove drivers from the roads?

Will he or won’t he tunnel under Los Angeles?

Few tunnels get as much public attention as just the idea Elon Musk has to tunnel under Los Angeles to avoid traffic:

After being stuck in heavy traffic in December, the billionaire came up with a plan to create a giant tunnel under Los Angeles to ease congestion.

‘Traffic is driving me nuts. Am going to build a tunnel boring machine and just start digging…’, he tweeted…

Excavators working for the entrepreneur have already dug a test trench at SpaceX’s headquarters in Hawthorne, Los Angeles, Wired reported last week…

‘If you think of tunnels going 10, 20, 30 layers deep (or more), it is obvious that going 3D down will encompass the needs of any city’s transport of arbitrary size,’ he told Wired last week in a Twitter direct message.

I have a hard time envisioning how this could become useful for the general public. Musk would have to figure out something pretty spectacular to get the cost and time down. Or, one tunnel could open but it would be prohibitively expensive to use.

And isn’t there also an issue of freeing up land for entrances and exits from these deep tunnels? (Los Angeles might be a bit different if the tunnels are primarily for going through mountain passes.)