The Folly of Double-Left Turn Lanes

By Dom Nozzi

There is a troubling, counterproductive “solution” that continues to be employed for addressing congested intersections – even in communities that are otherwise progressively promoting transportation choice. The “solution” is to add a second left turn lane to an existing left-turn lane when there is a perception that the number of motorists waiting in the single left-turn lane has grown too large.double left turn lane intersection boulder

Conventional traffic engineering claims that creating a double-left turn lane at an intersection is an “improvement” that will reduce greenhouse gas emissions by reducing congestion. And that a double left turn does not conflict with the transportation plan objective of promoting pedestrian trips.

On the contrary, I believe that double-left turn lanes will INCREASE emissions and will REDUCE pedestrian trips.

Double left-turn lanes cause serious problems for scale and safety for bicyclists and pedestrians, but have been shown to be counterproductive even if we are just looking at car capacity at an intersection. Adding a second left turn lane suffers significantly from diminishing returns. That a double-left turn does NOT double the left turn capacity – largely because by significantly increasing the crosswalk distance, the walk cycle must be so long that intersection capacity/efficiency (for cars) is dramatically reduced.

An example of an absurdity of this state of affairs is that the city of Boulder, Colorado was planning – in 2013 — to propose a tax on all property to raise revenue for road maintenance (there is a severe budget shortfall for such funds), yet the City seems eager, at the same time to build expensive and counterproductive double-left turn lanes.

This is probably because of the absurdity that transportation capital improvement dollars are in a separate silo than maintenance dollars, and that the former dollars are mostly paid by federal and state grants.  Of course, double-left turn lanes also destroy human scale and obliterates the ability to create a sense of place, but those are much more difficult arguments to make.

A colleague of mine — Michael Ronkin — adds that double-left turn lanes are an abomination. He adds that “they are a sign of failure: failure to provide enough street connectivity, so that when drivers do come to an intersection, it is gigantic, so it can accommodate all the left turns that had not been allowed prior to that point. Many trips on extra wide arterials are very short, and involve three left turns: one left turn onto the arterial and one left turn off the arterial: there trips could and should be made on connected local streets.”

How can a city such as Boulder claim it is short on transportation funding when it is building such counterproductive facilities? Double-left turn lanes…

  • Increase per capita car travel and reduce bike/pedestrian/transit trips.
  • Increase GHG emissions and fuel consumption.
  • Induce new car trips that were formerly discouraged (via the “triple convergence”).
  • Promote sprawling, dispersed development.
  • Discourage residential and smaller, locally-owned retail.

Boulder (and other cities) needs to draw a line in the sand: Place a moratorium on intersection double-left turn lanes and eventually removal of such configurations. Double-lefts are too big for the human habitat. They create a car-only atmosphere.

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State Departments of Transportation: Are They Always the Enemy of Our Communities?

By Dom Nozzi

What a fiasco. What a charade…

I served on a regional transportation advisory committee in Gainesville, Florida in the first decade of the 21st century. One particularly meeting – emblematic of so many of the meetings with this particular committee — was extremely tense and emotionally stressful.

At nearly all of the meetings I had been to since I was assigned to that committee a few years earlier, there were hostile exchanges and questions/rebuttals between us local folks and the Florida Department of Transportation (FDOT) staff. It was a typical meeting where FDOT was laying out their latest plans — for destroying Gainesville.

Ruinous plans are the norm for nearly all DOTs I know of throughout the nation.

At this particular meeting, we had a rather crowded agenda chock full of FDOT projects to “improve” Gainesville and otherwise make the city more “safe.”

A typical aspect of my service as both a town planner and a member of this committee is that I tend to be the “lone ranger.” The only one who has the courage and (apparently) the awareness to point out the elephant in the room. At this meeting – so much like many of the meetings I attended — I was the sole “no” vote (out of the 15 members) on 10 of the 11 projects on our agenda that day.

The usual DOT proposals for “improvements” and “safety”: Several new turn lanes. Resurfacing huge roads. Speeding up traffic.

highway multi-lane

The usual plans, in other words, to incrementally move Gainesville toward a south Florida future.

On two of the projects, FDOT wanted to resurface big, multi-lane monster roads. In the committee discussion, I confirmed with the City traffic engineer that these two road segments were way over capacity in size. Only a tiny handful of cars used them each day.

No-brainer candidates for seizing the opportunity during resurfacing to restripe these overweight five-laners to 3 lanes, I thought. As usual, my suggestions were met with derision, scoffs, nervous chuckles and, ultimately, deathly silence. Discussion quickly changed to other “more important” ideas such as adding a few trees or shrubs. No one made a comment about my proposed diets.

One of the items was a discussion about FDOT plans to essentially buy the front yard of some folks on the major road to add bike lanes. Taking land was needed to install bike lanes and straighten out the road (which, of course, would speed traffic and reduce safety).

As an aside, the redesign of this road was originally intended to primarily improve safety, but again, we only care about car safety at high speeds, not pedestrians, bicyclists or transit users. And to add insult to injury, the location was next to a large university campus, where there were enormous volumes of pedestrians, bicyclists, and transit users.

In any event, I pointed out that as a long-time bicycle commuter who had traveled that segment of road thousands of times, it was my opinion that it was, by far, the most crucial bike lane installation need in the county — particularly because it was next to a major campus, and the lack of bike lanes was very dangerous because it was a road pinch point where cars drive extremely closely to bicyclists at relatively high speeds.

Even for experienced bicyclists such as myself, that location was exceptionally dangerous.

So I told the committee that while I did not at all support the FDOT “solution,” adding the lanes there was essential. I pointed out, hopelessly, that the only reasonable design solution was to go back to the design that was nearly approved a few years ago — to remove one of the three travel lanes and create two-way traffic (one lane in each direction) and turn pockets — essentially creating a very pedestrian-friendly, bike-friendly, neighborhood-friendly, low-speed design. We would then have plenty of room for bike lanes without the need to take two-thirds of a front yard of a home. My suggestion was met with silence and the topic quickly changed to something like…oh, I don’t know…the paint color to be used on the road signs.

Another aside: it should be noted that FDOT staff always gave the citizen advisory committee pure engineering drawings. In other words, drawings that contain a vast, complex web of hundreds of solid and dashed lines and dimensional measurements that are completely irrelevant and undecipherable to a lay audience trying to make a decision about the project. As in meetings past, I pointed out at the meeting that it was completely impossible for me to figure out anything about what was being proposed on most of the projects. The drawings were a cluttered, jumbled mess.

If FDOT was seeking to hide what they were doing on the projects, the drawings they gave us were a perfect way to do it. For several of the items, I began the conversation by asking FDOT to tell me, in plain English, what on earth they were proposing, since I had spent days unsuccessfully trying to decipher the packet we’d been given. On a number of the drawings, I had no idea what was being proposed. And I’m a professional town planner. Even the City traffic engineer had to ask FDOT staff at the meeting what was being proposed on a few of the drawings. One certainly has to wonder if FDOT deliberately gives the committee engineering drawings knowing that only geeky engineers could make heads or tails of what is being proposed.

The committee was an embarrassing joke, and I made that known to my planning department supervisors a number of times since being appointed (asking my supervisors more than once to be taken off the committee). All the committee did was argue heatedly for window-dressing trivialities such as asking FDOT for a few more trees or shrubs — all to make driving a car more aesthetically pleasing to the motorist speeding by at 45 mph.

No thought was ever given by this garden club committee to designing streets for functional improvements. No thought or care was directed toward the needs of pedestrians, bicyclists, or transit users — in part because there was very little knowledge of what those sorts of travelers needed. But all of us sure knew how to design for faster driving by a Ford sedan, though…

And FDOT staff regularly became quite defensive about their projects, or said the trivial little landscape things asked for were “outside the scope of the project.”

Sometimes, though, their proposed destruction of Gainesville was obvious even to them, and they would ease their guilty conscience by throwing the city a few more trees into the project to put a band-aid on their latest atrocity.

It was a complete waste of my time.

And humiliating, because just by being there, I was implicitly and erroneously sending a message that I thought the items that were pushed by the majority of the committee was anything more than insignificant.

I came to learn that it was a waste of time to make motions for functional and effective design strategies, since I was never able to even get a second to a motion.

Gotta get back to arguing for another crape myrtle…

And to add extreme insult to all of the above, it was announced to the committee during the meeting that  the fearless governor at the time (JEB! Bush), had a few hours earlier just signed legislation which allowed FDOT to exempt itself from local rules. “No stinkin’ local regs are going to stop us from ramming a freeway through your town, boy!”

One has to wonder what point there would then be to having a “design team,” or even a regional transportation planning organization made up of local elected officials. Now even the nearly meaningless landscape and sign rules of the local community could be ignored.

FDOT already had the defacto power to trump local laws. Now it was official. I wondered if they were going to even tell us locals about their plans to “improve” our roads in the future, before their bulldozers show up…

As Andres Duany has pointed out, state DOTs have been more destructive of southern cities than General Sherman and the Union Army during the Civil War…

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Does the Price of Gasoline Modify Travel Behavior?

By Dom Nozzi

Studies show that American demand for high-priced gasoline is extremely inelastic (that is, Americans are willing [compelled?] to buy gasoline at their current promiscuous rate regardless of how high the price goes).

Why inelastic?

Because it is currently so incredibly rational to drive a car, even high-priced gas has only a relatively minor impact on changing travel behavior. After all, driving gives you extreme comfort, freedom from criminals, status, speed, convenience, heavy government subsidies, etc. By contrast, taking the bus, walking or bicycling requires one to recklessly and irrationally avoid all these wonderful benefits and instead, risk your life. As for “putting up with extra time,” studies show that Americans hate congestion almost as much as they hate density (which is a related problem in their minds). That is why we have a NIMBY epidemic, and why Americans hardly blink when their federal elected officials spend hundreds of billions of tax dollars each year to make cars happy (less burdened, in the very short term, by congestion, that is). It is also why, at the local level, Americans show “road rage” to the point of shooting people who make a left turn too slowly, and only elect commissioners who promise to spend all our local tax dollars to widen all the roads. I’ll never be mayor…

For all these reasons, I recommend “planned congestion” as a very effective aversive technique for car travel. “Planned congestion” is a tool with which a community makes a conscious decision NOT to widen roads/intersections or synch traffic signals, or engage in other conventional methods to “reduce” congestion.

Significant restrictions and higher prices for parking are also relatively effective ways to influence travel behavior. In Gainesville, Florida, very high parking costs and parking inconvenience on the University of Florida campus led to a nation-leading increase in bus ridership by UF students in the late 1990s.

As Donald Shoup points out, higher priced parking overwhelms higher priced gas in terms of impact on your pocketbook. After all, even with a gas guzzler car and gas that costs, say, $4 per gallon, howred-gas-pump-2 much would it cost to drive across town? But look at how quickly the price of that trip goes through the roof if we jack up the price of parking from, say, $1 to $10 per time parked across town (which is quite fair, given the public and private costs to provide parking).

This is not to mention the highly effective nature of “congestion fees,” in which you charge motorists fees based on when they are driving on major roads that tend to become congested, and even better, to charge fees that vary throughout the day (higher fees charged when the road is more congested).

For the record, I am not recommending that Americans “give up their cars.” I just want the cars to behave themselves — by driving more slowly and attentively in towns, and by having their drivers pay their fair share.

Fairly priced parking, parking scarcity, and congestion fees are very durable (in terms of modifying behavior), if designed correctly. They effectively send a very loud signal each day: If you choose the socially irresponsible, unsustainable travel behavior, you will pay through the nose. If not, you are free from such payments and can instead use your hard-earned money to spend a romantic weekend in Paris…  The message is especially clear if you see your fellow citizens zipping along in the tolled or high-occupancy vehicle lane next to your bumper-to-bumper congested “free” lane, or if you see your co-worker chuckling over his/her higher paycheck because he is not needing to pay for his workplace parking space with his paycheck, since he/she gets to work by bus, and has “cashed out” their “free” job site parking space.

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The Shocking Number of Street Segments in Town Center Boulder that are Off-Limits to Bicyclists

By Dom Nozzi

What are the factors that induce people to bicycle?

Two of the most important are relatively short travel distances, and relatively slow motor vehicle speeds.

Given this, the town center of a community should be one of the most popular, welcoming places to ride a bicycle. And indeed, bicycling in a town center is very often the most popular place in a city for bicycling in many communities across the U.S.

I have lived in the Mapleton Hill neighborhood in Boulder for five years now. The neighborhood is adjacent to the Boulder town center. Because I am a daily bicycle commuter, I am bicycling in the Boulder town center nearly every day.

Much to my surprise (given how often Boulder is recognized as a bicycle-friendly community at the national level), the Boulder town center is extremely inhospitable to bicycling.

I will discuss the factors that make this so, and end with a few recommendations about how the town center can be made much more safe, popular, and welcoming for bicyclists.

Some Important Obstacles to Bicycling in Boulder

As most all of us here in Boulder readily recognize, high-speed streets with more than three lanes are exceptionally hostile to safe, comfortable bicycling – especially when such streets lack bike lanes. Unfortunately for Boulder, the Colorado Department of Transportation, long ago, constructed two high-speed state highways that cut through the middle of the Boulder town center: Canyon Boulevard and Broadway. Due to the very high “speed differential” between motorists and bicyclists on these two highways (where motorists tend to drive at much higher speeds than bicyclists ride), both of these roads (what Charles Marohn would call “stroads”) are seemingly suicidal, nearly impossible corridors for even the most experienced, brave bicyclists to ride for more than 50 feet or so.

Another unfortunate town center street system decision made in Boulder long ago was to convert a great many two-way street segments into one-way operation. One-way streets create enormous problems for bicyclists. Because they reduce “friction” for motorists, they tend to strongly induce excessive levels of inattentiveness, higher speeds, and impatience on the part of motorists, and such factors can be quite a dangerous recipe that often produces unsafe motorist behavior. Healthy town centers depend on slower speeds, retail health, and “agglomeration economies,” and one-way streets substantially undercut each of these needed attributes.

An additional problem with one-way streets — particularly for bicyclists — is that they tend to induce frequent, dangerous “wrong-way” travel, as many people (especially bicyclists) decide it is just too inconvenient to travel blocks out of their way to get to a destination. Instead, many will simply ride the wrong way on a one-way street (at least for a short distance).

Because one-way streets, in recent decades, have very clearly been seen by many of us as detrimental to town center health, a growing number of cities are converting their one-way streets back to two-way operation.

An Inventory of Streets Off-Limits to Bicycling

In my five years of bicycling through the Boulder town center, it has become obvious to me how difficult it is to bicycle in the town center. Recently, I decided to prepare an inventory map of street segments in the Boulder town center that are, in effect, off-limits to bicycling. The attached map shows in red those town center street segments that are inhospitable to bicycling – either because they are Boulder town center streets hostile to bicycleshigh-speed state highways or one-way street segments.

As you can see, a rather large percentage of street mileage in the Boulder town center is off-limits to bicycling. Again, if any place should be comfortable and heavily used by bicyclists, it should be a lower-speed, compact town center. Yet in a city that regularly is given recognition for being “bike-friendly,” town center bicycling in Boulder is shockingly very difficult and dangerous.

Interested but Concerned

Admirably, Boulder now strives to find ways to encourage the very large number of citizens who are “interested but concerned” about bicycling to become more regular bicyclists. Many experimental designs and policies are now being tested in Boulder as the City strives to create an environment where those citizens will be more likely to ride a bicycle. Indeed, as can be seen in many European cities, town centers tend to be the place where many of the “interested but concerned” bicyclists can be found.

This is not surprising, since town centers tend to offer the slower speeds and shorter travel distances that attract such bicyclists.

Unfortunately, the street segments in red on the attached map are strongly undercutting this worthy objective of encouraging the “interested but concerned” citizen to ride a bicycle.

A Lesson from Copenhagen

In the 1980s, Copenhagen’s bicycle planners observed that large numbers of bicyclists were using the same major streets that motorists were using. Planners convinced the City to build a high-quality bicycle route on a slower-speed, less-used parallel street.

To the surprise of planners, hardly any bicyclists used the parallel routes. The planners realized that bicyclists wanted to follow the same ‘desire lines’ as motorists – that is, choosing the most direct route. The result was a sea-change in modern bicycle planning, where efforts to direct bicyclists to parallel streets changed to efforts to accommodate bicyclists along the same major streets that motorists preferred.Bikecultureincopenhagen

Copenhagen realized that you can’t tell bicyclists (or pedestrians) where to go. Rather, bicyclists (and pedestrians) will show you where they want to go and you should listen to them and plan accordingly. Unfortunately, Boulder has not yet fully adopted this approach, as can be seen by City efforts to use the parallel 13th Street and 9th Street as places for bicyclists to ride, instead of Broadway.

Some Suggestions for Making the Boulder Town Center More Bicycle-Friendly

  1. I am often the first person to point out that it is very difficult, if not impossible, to successfully mix bicyclists with pedestrians on a sidewalk or a path. In general, we should not try to mix bicyclists with pedestrians. However, I believe it was a mistake for Boulder to outlaw bicycling on sidewalks along commercial streets where the sidewalk is not designed or designated for bicycling. On each of the street segments shown in red on the attached map (where bicycling is relatively dangerous), it is incumbent on a community which wishes to promote bicycle travel (especially for those who are “interested but concerned”) to allow slow-speed bicycling on sidewalks. Repealing this counterproductive law would be TEMPORARY, as I would recommend that the prohibition be re-instated when or if the “red segments” shown on my map are redesigned as I recommend below. In addition, during this temporary period where bicyclists would be allowed on sidewalks until the street is re-designed, city rules would require that bicyclists ride responsibly, courteously, and relatively slowly on the sidewalk (preferably, bicyclists would ride at pedestrian speeds). By not allowing bicyclists on sidewalks, the “off-limits” streets create a tremendous amount of inconvenience for bicyclists, as it can mean that the bicyclist must ride one to three blocks out of her or his way to reach a destination.
  2. As noted above, town center health depends on slower speeds, agglomeration economies, and human-scale design. Canyon Boulevard and Broadway, as high-speed state highways, dramatically undermine these necessary attributes, and make bicycling a dangerous, impractical form of travel on those corridors. A low-cost, effective treatment for improving the health, safety, aesthetics, and pleasure of the Boulder town center is to re-purpose each of these highways to be three-lane streets. Doing this would slow motor vehicle speeds to speeds more conducive to both bicycling and a healthy town center, and would create needed space for such beneficial treatments as on-street parking and bike lanes.
  3. Boulder should join the growing revolution where cities throughout the nation are converting their one-way streets back to two-way operation. Doing so is a quick, effective, low-cost way to dramatically improve town center health, comfort, and safety. Motorists would drive more slowly, more attentively, and more patiently.
  4. Intersection controls should convenience bicyclists, not motorists — particularly in the town center. Stop lights and stop signs, even in relatively bicycle-friendly Boulder, are surprisingly inconvenient for bicycling. I have noticed that signal lights in the town center are timed for motorist speeds. In a community seeking to promote transit and bicycling, signal lights should rather be timed for buses and bicyclists. In addition, Idaho has revised its state laws so that bicyclists are allowed to treat red signal lights as stop signs, and stop signs as yield signs. Doing this would make bicycling much more advantageous (an important way to encourage more bicycling). Boulder should seek state authorization to apply the Idaho law here in Boulder (if not statewide).

In sum, Boulder’s town center is shockingly off-limits to bicycling. Fortunately, there are ways for the City to correct that – particularly as a way to encourage the large number of “interested but concerned” citizens to become regular bicyclists, and to substantially grow the overall number of bicyclists in Boulder.

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Police Arrest Motorist AND Bicyclist

Police: Man arrested for trying to run down cyclists

May 22, 2004

By ALICE WALLACE, The Gainesville [FL] Sun

Police say the man was angry because the cyclists weren’t riding single-file and began yelling at them.

Gainesville man was arrested Friday night after a road rage incident in which he tried to run down a group of nine bicyclists who were riding down E. University Avenue in the area of Newnan’s Lake, according to the Alachua County Sheriff’s Office.

No one was injured in the incident.

Lt. Jim Troiano with the Sheriff’s Office said George Hastings, 60, of Gainesville, was driving east in the 7000 block of E. University Avenue late Friday night when he encountered a group of nine bicyclists riding two-by-two along the two-lane road. Troiano said Hastings was angered because the bicyclists weren’t riding single-file and began yelling at them through his car window.

The bicyclists yelled back at Hastings, Troiano said, which angered Hastings further. He pulled in front of the bicyclists and slammed on his brakes, nearly causing the riders to crash into his 1998 Taurus, Troiano said.

In retaliation, one of the bicyclists caught up to Hastings’ vehicle and punched him through his open car window, Troiano said.

“That really made the guy mad,” Troiano said. “So he took off and then conducted a series of U-turn maneuvers. He was trying to run over these bicyclists.”

Troiano said Hastings was essentially chasing the bicyclists around the road for a while, running up on the bicyclists and then turning around each time he missed them.

“He was driving all over,” Troiano said. “He almost ran over one of the bicyclists. The biker was barely able to veer away from the guy’s path.”

Eventually, Hastings stopped his vehicle and began exchanging blows with the bicyclist who had punched him through his window, Troiano said.

While the two were fighting, a bystander who was out in his front yard saw the commotion, called law enforcement and then quietly went and turned off Hastings’ car and took the keys so he would not be able to leave until law enforcement arrived.

When the Sheriff’s office arrived, deputies arrested Hastings on three aggravated assault charges. Troiano said they are also sending charges to the State Attorney’s Office in the form of a sworn complaint charging the bicyclist who punched Hastings with burglary and battery. He said the bicyclist is being charged with burglary because he reached into Hastings’ vehicle. “We’re definitely holding blame on both sides, but the aggressor was definitely Hastings,” Troiano said. “He could have easily killed several of those bicyclists.”

My thoughts about the above news article:

  1. As a bicyclist, I can confirm that this sort of aggressive, dangerous, homicidal motorist behavior against bicyclists happens all the time.
  2. The story is a good example of something that is highly annoying to the bicyclist: Nearly all motorists haven’t a clue about the rules of the road or the safest way for bicyclists to ride their bikes. In this case, the motorist was enraged that the bicyclists were riding two-by-two instead of single-file. While single-file sometimes allows the motorist to avoid being delayed by bicyclists (as he can get around them easier), it also happens to be a form of bicycling that is dangerous to bicyclists, which explains why they were riding two-by-two. Two-by-two forces the motorist to be more careful. The motorist must pass by getting into the adjoining travel lane briefly to get around the bicyclists, rather than trying to squeeze by the bicyclist in the same travel lane. Two-by-two also makes the bicyclists more visible to the motorist. It is a form of safety in numbers.
  3. I am aghast that the police found it necessary to arrest both the homicidal motorist AND the bicyclist.

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Curbing the Expectation of Driving at High Speeds

By Dom Nozzi

Many of us who seek to make our world more conducive to happy people rather than happy cars are adamant about the importance of slowing car speeds in communities.

Residential streets typically do not promote the problem of high-speed, free-flowing traffic, but sometimes they do act in such a way when they are used for “cut-through” trips or if they are relatively large neighborhood streets which “collect” traffic fed from smaller streets in the neighborhood (usually called “collector” streets).

Lowering the average motorist speed is one of the most essential ways I can think of to improve quality of life. And the most effective way to do that is through calming strategies which design the street to force slow car travel. It is critical that we LOWER THE EXPECTATION of motorists to be driving at high speeds. High speed car travel in a community should not be considered the “default” way for a motorist to travel.

Tragically, conventional traffic engineers have designed our streets for the past 100 years to promote high-speed travel – even on what should be quiet, low-speed streets. The result is that too many motorists now believe that relatively high-speed driving is the norm.

If we instead start designing our communities so that, eventually, most streets in a community are designed for slow car travel, general expectations will evolve so that a motorist realizes that the normal manner of driving is to drive slow (except on interstate highways, of course). With such an expectation, there will be significantly less road rage (and related hostile driving) in calmed areas, because the motorist EXPECTS to drive slow.

Designing streets for slow speeds is particularly important on residential streets, because such streets are the places where we most expect children and seniors to be, and where people are in homes and bothered by the noise of high-speed car travel. We also need to slow cars on the BIG roads in our community to ensure we solidify a general motorist expectation that they are driving in a slow speed community.

“Road rage” and fast driving are NOT genetically programmed into humans. A slow-speed community is NOT unrealistic.

In a discussion about slower car speeds, it is important to note that speed limit signs have little or no impact on how fast a motorist drives. Average driving speed on a street is dictated by the “design speed” of the street. The conventional traffic engineering philosophy is to assume that safety is best achieved by designing the “forgiving” street. That is, to design the street so that the motorist is “forgiven” if they, say, drive too fast and lose control of their car.

What this means is that the street is made wide and obstructions are kept away from the shoulders so that a fast, out-of-control motorist will not smash into anything.

Unfortunately, this fails to take into account the motorist psychology. If you design a street for safe driving at 40 mph, the average motorist will drive 40 mph, even if the posted speed limit signs say 30 mph, because average driving speed is determined by the maximum speed a motorist feels comfortable driving.

Typically, this philosophy means that a street with a speed limit of 30 mph has been designed with a “design speed” of 40 mph. We should not be surprised when a large number of motorists drive 40 mph on such streets. Enforcement is nearly impossible, short of a police state.

Therefore, in my opinion, the “forgiving street” philosophy gives us LESS safety due to higher speed (and more inattentive) driving.

The effective solution for slowing cars is to “retrofit” our streets (including residential streets) with calming designs that force cars to slow down (which is why things like speed humps are often called “sleeping policemen”).

However, “vertical” treatments like humps are almost never, if ever, appropriate for streets (including residential streets) – particularly those that are on designated emergency vehicle routes (where calming needs to be carefully designed to not excessively impede such vehicles).

In the case of such routes, “horizontal” calming is usually called for. Horizontal treatments include such things as curb extensions or other forms of street narrowing, as opposed to “vertical” calming like humps.

Does Traffic Calming Increase Air Pollution?

A common objection to traffic calming is that air emissions will increase due to “stop and go” traffic that is induced by calming. But this concern makes the mistake of  being overly reductionist. Peter Newman and Jeffrey Kenworthy effectively point out why reductionism in this case leads to erroneous conclusions. Newman and Kenworthy correctly point out that those who fear higher emissions due to calming forget about changes in motorist behavior that occur with calming. Reductionist thinking in this case only looks at what is coming out of a tailpipe of individual cars.

But Newman and Kenworthy, take a broader and more accurate view by pointing out that changes in travel behavior (caused by higher development densities, shorter travel distances, congestion, calming, etc.) completely swamp any air pollution gains that can be realized from individual cars that have less stop-and-go travel.

I will grant that it is possible there will be “micro-level” increases in air pollution levels due to calming. But at the “macro” (community) level, I’m convinced there is a net reduction in air pollution. That is, there is LESS air pollution at the community level.

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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…

curb radius large vs small

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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