Tag Archives: inattentive driving

What Do I Think of the Diverging Diamond Interchange?

 

By Dom Nozzi

Febuary 2, 2017

Superior, Colorado built a “diverging diamond” interchange that opened in October 2015. It was only the second such interchange to ever be built in Colorado. Traffic engineers are imagessinging its praises throughout the nation. A newspaper article appearing in the February 2, 2017 edition of the Boulder Daily Camera fawned over the fantastic new addition to the region’s transportation system.

I am not joining the engineers or the newspaper in their love affair with the design.

Instead, I find such designs a colossal waste of money – money that could have been used for, say, transit. They are also a colossal waste of land. An entire city could fit inside one of these intersections.

The diverging diamond is a boondoggle for those reasons. But it is also a blunder because they promote increased per capita car travel. Why? In part because they are nearly 51df393d218c6-imageimpossible to cross by foot or bicycle. And in part because in the long run they will further disperse land development in a more sprawling way. Those increased distances will make it increasingly impractical to walk, bicycle or use transit.

Ironically, the major justification for the car-only design is that it briefly reduce intersection congestion, which will initially save a few seconds of motorist time (think of the fiscal irresponsibility of spending millions of public dollars spent to save a few seconds temporarily). Ironic because by artificially inducing more car trips than would have occurred had the diverging diamond not been built, the design will lead to MORE traffic congestion and MORE time delay for motorists in the long term (both at their location and areas in the region).

To hide the embarrassing fact that the millions spent ($14 million in this case) to briefly save a few seconds of time, the publicly proclaimed explanation is that it will improve safety. For the conventional traffic engineer, “improved safety” actually means that motorists can now drive faster and more inattentively with less fear of crashing. No mention is made of the fact that the intersection is much less safe for pedestrians or bicyclists, or that faster, less attentive driving is very dangerous for everyone.

The diverging diamond, therefore, is an excellent example of the century-long failure by conventional traffic engineers to understand induced car trips that are created by (briefly) reducing traffic congestion with these designs. There is a reason, after all, that many researchers repeatedly urge us to understand that it is impossible to build our way out of congestion. It is like loosening your belt to solve obesity.

But wait. There’s more.

Not only is the diverging diamond a boondoggle in the above mentioned ways. It also damages our world by adding more auto emissions into our air (by increasing per capita car trips) and reducing potential tax revenues in the region (by encouraging dispersed rather than compact land use patterns).

Future generations will shake their heads in disbelief over why our generation built these monstrosities.

There is one tiny upside to this overwhelmingly negative idea: it produces future jobs for people hired to remove these mistakes after we regain our senses.

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Traffic Safety in Boulder

By Dom Nozzi

As a member of the Boulder Transportation Advisory Board, I am alarmed  by the recent uptick in serious injuries and deaths caused by vehicle crashes on roads in our area. I am ashamed that our community seems poised to respond with the same old song and dance.

Three factors are primarily responsible for enormous traffic safety problems that persist in Boulder.bike-car-crash1

First, roadways and intersections have grown enormous in size in Boulder. Roads such as Arapahoe, Canyon, Colorado, 28th Street, and Baseline now have such a large number of travel lanes and turn lanes that pedestrians and bicyclists must now cross a huge distance made more daunting by the high speed car traffic on these roads. Anything more than 3 or 4 lanes is extremely dangerous to cross, and these roadways now contain up to 7 or 8 lanes. This oversizing has been driven by an effort to promote “free-flowing” traffic – even at rush hour. Given the enormous size of cars (a person consumes 17 to 100 times more space in a car than in a chair), and the large number of regional commuters coming to Boulder each day, retaining “free-flowing” traffic — even at rush hour — is a recipe for finding yourself oversizing streets and intersections. Boulder has certainly done that. By doing so, Boulder now has a number of oversized roads that are too big for a city, too big for safe bicycling or walking, and too big to have any reasonable chance to achieve an emerging plan of “vision zero” for crashes (reducing the number of traffic deaths and serious injuries to zero). To put the oversizing problem in perspective, if we want to carry 50,000 people per hour in each direction of a road, we’d need one lane worth of road if they are carried by train, two lanes if carried by bus, and 18 lanes if carried by car.

Second, it is important to note that at the dawn of the auto age a century ago, nearly all American cities – including Boulder — adopted forgiving roadway design. Forgiving design “forgives” a motorist for driving too fast or not paying attention by increasing the width of travel lanes, adding travel lanes, and removing “obstacles” from the areas flanking roads (trees, buildings, etc.). The naïve thought was that this would reduce the number of things motorists would crash into.

The unintended consequence, however, was that this design significantly increased motorist speeding and inattentiveness, as a motorist tends to drive as fast and as inattentively as the roadway design allows. The result of forgiving design is that there is an epidemic in motorist speeding and inattentiveness – aggravated by the concurrent epidemic in sleep deprivation that causes most all of us to occasionally fall asleep at the wheel.

Third, for 100 years, nearly all US cities — every few years — have “renewed their efforts” to improve traffic safety. We “redouble our work” to institute the “Five Warnings:”

Warning signs are installed. Warning lights are erected. Warning paint is painted. Warning education is introduced. Warning enforcement is pushed.

After all those campaigns over the past century have been waged, what has been the result? We have, today, the most dangerous streets we have ever had. Clearly, the Five Warnings have been ineffective.

For several decades, we have been so successful in providing for fast, unobstructed travel by car that it has substantially undermined transit ridership, walking, and bicycling. “Danger” is an all-too-frequent reason given in surveys for not bicycling, for example.

Wide travel lanes and multi-lane roads exert a nearly irresistible influence over a motorist. Even motorists who are not inclined to drive fast creep up to highway speeds. Amplifying this problem: large numbers of drug- or alcohol-impaired drivers, sleep-deprived drivers, and time-starved drivers. These factors are a dangerous mix, as they induce a great deal of high-speed, inattentive, reckless driving.

As noted above, making a street “safer” too often increases vehicle speeds, which makes the streets less safe – particularly for pedestrians and cyclists. One result: a disproportionate number of serious injuries and deaths in Boulder are suffered by pedestrians and bicyclists. About 40 percent of all children killed in motor vehicle crashes nationally are killed while walking or riding a bicycle.

Measured by “years of life lost,” motor vehicles fatalities rank third.

Since 1930, over 30,000 Americans die in motor vehicle crashes annually.

This is appalling. And should be completely unacceptable to any civilized society.

The Importance of Traffic Calming

One of the most common requests by citizens to our Board is the need to reinstate the neighborhood traffic calming program that was defunded in the early 2000s. Speeding, cut-through vehicles are a serious problem for many neighborhoods. Such traffic discourages bicycling and walking, substantially increases noise pollution, endangers our most vulnerable (seniors, children, the handicapped, and pets), is a primary cause of loss of neighborhood quality of life, and fuels opposition to infill development.

Traffic calming, which is a street design that obligates motorists to drive more slowly and attentively, has been shown to dramatically improve street safety. Desirable design examples include traffic circles or roundabouts, curb “bulbouts” (which reduce the width of the street), and removal of travel lanes or turn lanes. Roadway geometry in safety-sensitive areas, such as schools, needs to keep speeds near 20 miles per hour. Traffic circles reduce crashes by 50 to 90 percent, compared to two-way and four-way stop signs and traffic signals, by slowing cars and reducing the number of conflict points.

Note that in general, “horizontal calming interventions” such as circles and neck-downs are more desirable than “vertical calming interventions” such as speed humps. Among other things, humps cause noise pollution problems and can dangerously impede fire truck and other emergency vehicle response times.

Motorists are more likely to collide with pedestrians at higher speeds. At 60 miles per hour, the field of vision of the motorist is two-thirds less than at 30 miles per hour. In addition, the probability of a pedestrian being killed is only 3.5 percent when a vehicle is traveling at 15 miles per hour, but jumps to 37 percent at 31 miles per hour and 83 percent at 44 miles per hour.

Despite the conventional wisdom, stop signs do not affect overall speeds or control speeding. Posting lower speed limits and enforcing them is not sufficient to achieve needed reductions in speeding. Modest physical reconfiguration of streets is the only reliable and cost-effective way to slow and control inattentive speeding.

Calming helps reduce neighborhood noise pollution. Higher speeds substantially increase noise pollution.

The Federal Highway Administration (FHA) notes that the importance of reducing traffic speed cannot be overemphasized, and has stated that traffic calming is one of the more cost-effective ways to promote pedestrian and bicycle use in urban and suburban areas, where walking and bicycling are often hazardous and uncomfortable. And as for children, Stina Sandels, a world authority on children and road accidents, says that the best road safety education cannot adapt a child to modern traffic, so traffic must be adapted to the child.

Fortunately, there are effective street design tactics to substantially increase road safety, and these methods can be deployed without significantly slowing emergency vehicle response times.

I urge Council to restore funding for neighborhood traffic calming. Since the City does not have the authority to introduce safe, speed-slowing designs on larger state roads, I urge Council to lobby the State legislature to give Boulder the authority to do so.

Summary

How about if we do something effective to improve traffic safety?

  1. What if, instead of pursuing the ruinous objective of maintaining “free flowing” traffic (even at rush hour), we start the process of shrinking the size of the many over-sized roads and intersections in Boulder to induce slower, more attentive driving? (not to mention a financially healthy atmosphere for retail, and a higher quality of life for homes)
  2. What if, instead of continuing the counterproductive “forgiving” street design paradigm, we revise Boulder’s street design manuals to obligate slower speed, attentive driving? (including a restoration of the Boulder traffic calming program)
  3. What if, instead of continuing the failed, century-long effort of using the “Five Warnings” — which amounts to a form of blaming the pedestrian and bicyclist victim — we put more of the onus on traffic engineers to design streets to obligate safe motorist behavior? How about if we return our transportation system to people, instead of our on-going effort to be a doormat for ruinous levels of car travel?

In addition to the above, I recommend more compact development in appropriate locations, sponsoring a transportation safety speaker series, and more street connectivity.

We have a duty to make Boulder streets much safer.

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The Forgiving Road

 

By Dom Nozzi

January 23, 2002

Why does it seem that Americans have such poor driving skills?

I believe I have at least part of the answer.

For several decades we’ve been designing streets and roads and highways to be forgiving. The “forgiving road” is one that “forgives” the driver if the driver commits a driving error. That is, being reckless, or high-speed, or inattentive no longer is followed by the “punishment” of consequences such as crashing into something. We’ve done enormous forgivingwork pulling buildings, parked cars, pedestrians, bicyclists, trees and other “obstructions” out of the way so that even an unskilled motorist can travel at high speeds without crashing into something.

This was thought to be a way to promote “safety.”

The hidden agenda for many, I believe, is to promote high speed travel by large volumes of car traffic.

Of course, what many of us now realize is that such a design promotes reckless, high-speed, inattentive driving because human psychology is such that a person tends to drive at the highest speed that still feels safe.

Since we tend to be busy and in a hurry, forgiving roads deliver lots of motorists who drive as fast as they can and multi-task while driving (drink coffee, talk on the cell phone, read, etc).

The result is an increase in crashes due to speeding, inattentiveness, and recklessness. Ironically, motorist safety declines, because the forgiving road condition motorists to be less attentive.

Is it any wonder that we are seeing what I believe is a growing number of inept American motorists throughout the nation?

 

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Run for Your Life When a Traffic Engineer Wants to Make a Road More “Safe”

By Dom Nozzi

Conventional traffic engineers (the people who have been designing our roads for the past century) often like to make the claim that their design strategy is to make the road more “safe.” The tragic irony is that a great many of their “safety” tactics actually make the road much less safe.

And that helps explain why today, we have an epidemic of unsafe, inattentive motorists driving at excessively dangerous speeds. What could be more ironic?

Here is an excellent, common example of how our roads become less safe in the name of “improved safety”:

A road intersection have what are called a “turning (or “curb”) radius.” This radius is a measurement of the tightness or width of the corner of the intersection. The following image illustrates a tight radius vs a wide radius…curbradius

Too often, the conventional traffic engineer will recommend a wider turn radius for “safety.” He or she will frequently state that a wider radius is needed to help improve pedestrian safety. Without a wider radius – the engineer will often claim—motorists will sometimes jump the curb, which would endanger pedestrians.

Nonsense.

What actually happens in the real world is that the wider radius allows most motorists to negotiate the turn at a much higher (and more inattentive) speed, and there is very little that is more dangerous than a motorist driving at excessive speeds inattentively. If a motorist “jumping the curb” was truly a problem, hardened bollards should be placed at the curb to to punish or otherwise discourage reckless, excessively speeding driving.

Another canard that the engineer often pulls out is that the wider radius is needed because the road is used by very large vehicles (such as buses or trucks). The large vehicle becomes what is called the “design vehicle” that the engineer uses to design the road geometries.

But again, the unintended consequence emerges. By enabling the large vehicle to negotiate a turn with a wider turn radius, we induce the high-speed, inattentive driving by the much more common passenger vehicle. Overall safety goes down as a result, because while a large truck jumping a curb is perhaps averted by the wide radius, such vehicles are quite rare, whereas the smaller passenger vehicles which are induced to drive more recklessly are much more common.

In a walkable downtown, it is ass backwards to use a large vehicle as the design vehicle for designing the streets. The pedestrian should be the design “vehicle” if a town center is to be designed for walkability. Using a large vehicle as the design vehicle utterly undercuts the objective of creating a safe, walkable street design for pedestrians.

There are much more appropriate strategies for dealing with large vehicles in a town center that is intended to be walkable. First, the effective turn radius can be made wider without creating the unintended consequences I mention above. This can be done quite simply by adding on-street parking close to the intersection. Or, the community can prohibit the use of large vehicles in the town center.

When conventional traffic engineers mention “safety,” watch out. Usually, it is just a smoke screen to grab the moral high ground at a public meeting concerning street design. Meanwhile, the man behind the curtain that we are not supposed to notice is designing the street for a single-minded objective: Higher motor vehicle speeds — which, of course, degrades our safety and quality of life.

Tactics such as wider intersection turn radii usually fall under the category of the conventional “forgiving street” philosophy, whereby we “forgive” reckless, high-speed, out of control driving by eliminating things that motorists might run into, such as trees, pedestrians, buildings, parked cars, etc.

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Conventional, Forgiving Road Design Reduces Road Safety

By Dom Nozzi

Conventional “forgiving” road design strives to forgive bad drivers. Engineers who subscribe to conventional road design look at road crash data that shows many crashes have occurred due to excessive speed, or due to the driver using a cell phone, or putting on make-up.

The solution seems obvious: Design roads so that if the driver is driving too fast, or is using his cell phone, or is putting on her make-up, there will be less chance of a severe crash.

Unfortunately, this obvious solution results in less road safety. Why? Because conventional engineers have forgotten about human nature. If you design a road to forgive a driver for engaging in reckless driving, you encourage people to drive too fast and drive too inattentively. Human nature is such that most people drive at the highest speed that feels safe (regardless of what the speed limit sign says). Because we are so busy these days, we try to find more time in our day by driving faster and by multi-tasking (talking on a cell phone while driving, for example).

Engineers who have been designing the forgiving road for the past 60 years have therefore been busy widening roads, removing on-street parking, removing street trees, and pulling buildings away from the street — all in an effort to minimize the chance of a speeding, inattentive driver crashing into something.

But it does not take rocket science to realize that the forgiving road has the unintended consequence that most of us will drive more dangerously. We drive faster and more inattentively because we can do so more safely now.

The solution is clear, yet counter-intuitive: We need to design roads so that we force drivers to pay attention and slow down. On such roads, a much smaller number of drivers will speed or talk on a cell phone, because it is too risky to do so on a street that is not forgiving. If you don’t pay attention, or if you speed, you will suffer consequences. On roads that are not forgiving, we breed more attentive drivers. And more skilled drivers.

Forgiving roads with too many “safety” features, by contrast, breed a decline in driving skill. It is therefore no surprise that there seems to be a large a growing number of drivers who drive poorly. Now we know why American drivers are among the worst drivers in the world.

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