chokers - effective traffic calming or roadway hazard? 1

My question is why the heck are you building residential streets with the same width as a rural principle arterial? No wonder people are asking for traffic calming!

I see no problems with a 28' choker. After all, it provides two 14' lanes, which is still wider than the standard lane width. I fyou wanted to, you could stripe it as two 10' lanes and an 8' parking lane.

Many of the things we do have drawbacks. An axample is guiderail. You can expect more crashes to occur at a location after guiderail is installed. Why? Because it is closer to the road than the object if protects traffic from.





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"...students of traffic are beginning to realize the false economy of mechanically controlled traffic, and hand work by trained officers will again prevail."

Wm. Phelps Eno, ca. 1928

I agree with ACtrafficengr on this.

We used 28' curb-to-curb for our large residential streets intended for on-street parking. Surely it's only a roadway hazard if it's not safe to negotiate at the speed limit, which is presumably 20-30mph.

The chokers in Europe usually only allow one car to pass regardless of direction. The Dutch, I believe, experimented with removing all traffic signs as a traffic calming measure -- surprisingly successfully. Their theory was that, if drivers have to figure out what's going on, they'll drive more cautiously.

Regarding the local street cross sections, many California cities have similar requirements. The 60' R/W provides 10' from face of curb to the R/W line for a sidewalk and planter strip, with 40' curb-to-curb. That means 20' from C/L to face of curb which allows for on-street parking on both sides of the residential street and a 12' travel lane in each direction (unstriped of course). We also have a 54' R/W standard which is the same but reduces the sidewalk pattern to 7' thus not including street trees. If we were to reduce the width, we would not allow on-street parking which makes a single-family home undesirable since where would people park their cars?

I just realized I didn't state my point about the guiderail.

The point is, not everything is judged on whether it is a hazard. For many things we do, the relevent question is, "Do the safety benefits outway the safety costs?" In this case, does the reduction in crash severity and(hopefully) frequency due to reduced speeds outweigh the costs of inattentive drivers running into the choker (plus construction costs, including DIs on the uphill side).



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"...students of traffic are beginning to realize the false economy of mechanically controlled traffic, and hand work by trained officers will again prevail."

Wm. Phelps Eno, ca. 1928

Our standard for residential streets is 26 feet back of curb to back of curb with a 40 foot right of way. We allow parking on both sides of the street with a posted speed limit of 25MPH. Several of the older sections of town have 20 foot streets, again parking is allowed on both sides.

If people are dumb enough, and yes I know that some are, to park directly across from someone and block the street, then a resident just has to call the police.

Heck, the street I live on was built in the 50's and is only 18 feet wide.

Also, with the 40 ft. right of way, we also have sidewalks on both sides with trees between the street and walk.

"Traffic Calming" is a flash in the pan. It's one of those things that increases inefficiency. It reminds me of the Conquistadors' method of hobbling Indians so they wouldn't run away. The typical citizen sees it as nothing more than a pain.

I believe that you'll find that residents of the streets that receive the traffic calming measures are immeasurably pleased with it.

"Rat running" is a big problem through neighborhoods for residents, while a convenience to many more people who are using the rat runs. Looking from the perspective of society as a whole, one might say that traffic calming benefits few and harms many... until a child is killed by a racing motorist.

Subdivision designers should be careful not to design roads that will be attractive as thoroughfares I guess, but it is challenging, particularly in subdvisions of 500+ lots.

I'll bet not most of them. The ones that would be happy with it live near the entrance - the ones that aren't are the ones who live in the middle and now have to waste another 5 minutes per day on the road...

It's an indirect bureaucratic answer to a responsibility problem.

LCruiser,

You are correct that traffic calming is not a perfect solution to a real problem. But then there is not a perfect solution. It is easy to say that the real solution is that people be responsible and drive an appropriate speed for the type of road and area that they are driving in.

However, experience shows that many people in this country do not do this. When people choose not to be responsible it is the job of government, specifically police departments and public works, to make people behave in a responsible fashion. The police can right tickets; studies have shown that this is generally not very effective. Public works (and design engineers) can make the roads less attrictive to drivers going faster than the prescribed speed. Does this make the road less convient? YES. That is part of the price that people in a society have to pay.

"Public works (and design engineers) can make the roads less attrictive to drivers going faster than the prescribed speed. Does this make the road less convient? YES. That is part of the price that people in a society have to pay."

Not true. Other people do not have to pay that price. Enforcement is the issue, not everybody's speed. A percentage of drivers will drive at an unsafe speed. You slow the safe speed of the throughfare, people slow down, but you still have people driving unsafe speeds - they're just slower because the safe speed of the road is slower. The answer is not to slow down everyone by making the road less safe at a given speed, the answer is to slow down the people driving too fast. "Traffic Calming" is a misnomer. It's true that enforcement is not the ideal answer, but it's certainly much closer to an ideal answer than slowing *everybody* down. We're talking urban environments with children running around, not freeways where enforcement is a part of the problem and not part of the cure.

"You slow the safe speed of the throughfare,... "
Wasn't the original poster asing about a residential street? Many traffic calming techniques are not meant to be used for collectors and arterials.

I was talking to a small city police chief last week who said his department has gone from 15 policemen to six. All the other policemen in the room nodded in agreement. We can't rely on enforcement anymore.

There are many places where roads are innappropriatly designed for their use (such as 40' wide residential streets). Blaming speeds on lack of enforcement when poor design plays a role is unprofessional.

The design speed concept evolving in ways I think are related here. Minimum design speed is on the way out. Consistent design speed between adjacent segments is gaining currency. With a minimum design speed of 30 mph, you can have a 30 mph curve at the end of a 4 mile tangent, and it meets your standard. The new approach gives you a red flag for sudden changes in effective design speed between adjacent segments.

As these changes progress, I expect a shift away from speed humps and towards alignments and cross sections that promote appropriate speed for the road's functional class and area.

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"...students of traffic are beginning to realize the false economy of mechanically controlled traffic, and hand work by trained officers will again prevail."

Wm. Phelps Eno, ca. 1928

Residential streets are designed for residents to access their homes. The trouble comes when the arterial and collector streets become congested and non-residents seek rat runs through residential areas. These are the people driving too fast. Mrs A. will slow down if she knows that little Timmy usually plays in the street at 4pm, but non-residents neither know that nor care.

You could fault the designer or the subdivision regulations for turning residential streets into large speedways; you could fault the developer for favoring a longitudinal subdivision design that maximizes his number of lots.

Traffic calming has been shown to reduce accidents, particularly fatalities. It also reduces traffic noise. Residents who are displeased with traffic calming usually weren't consulted on the planning and design of the calming measures, which frequently results in unsightly traffic calming, instead of more attractive measures (landscaped islands, etc.). I would wager that traffic calming would raise property values, but I didn't find any evidence for this.

"Traffic calming has been shown to reduce accidents, particularly fatalities."

Ultimately non sequitur. Making people stay at home also reduces accidents...

The question is how to make streets safe and not increase travel time. Some people don't mind additinal travel time. However, some people have a life.

I suspect that you would feel differently if people were rat running on your street and it was your kids playing basket ball in the street.

Some people have a life, and others have it stolen by a speeding motorist.

OK, there has been plenty of good input and some digressing from the topic. In our City traffic department, we actually get some complaints about the narrower residential streets. In one case of a 36' wide street, people are asking us to paint red curb on one side to eliminate parking and make it a safer roadway for the motorists. To me the best traffic calming measures are to eliminate long straight runs in the subdivisions, although they do create the most lots and putting in some bends causes the developers to lose lots. We ask for 90 degree knuckles to break up the streets and even at times add compact roundabouts at T- or 4-way intersections. I don't feel open to a residential street width of less than 36 feet curb-to-curb where parking is allowed on both sides. Here's why: the Fire Department needs a 20-wide clear area and then parking takes 8 feet on both sides. Now, back to the original post...the question is whether an artificial constriction at one point in the road, say necking down the street from 36' wide to 28' wide with a 2' wide raised median island in the middle is good for traffic calming or whether it could be construed as a hazard. I am concerned that after a few accidents and claims, the City Risk Management and attorney's office would require Public Works to go and pull them all out. Thanks

You're contradicting yourself. If the fire department requires 20' clear way, how can you put in the 2' raised median?

More importantly, however, why on earth does the fire department require 20' clear way? Their vehicles aren't that wide and if you're designing streets for traffic to pass around a fire truck during a home fire then those are the most ridiculous design criteria I've ever encountered. The former city engineer I worked with didn't even design his water reticulation network for peak flow and fire flow simultaneously: "I figure if a house is burning down, people will be on the street watching it, not taking a shower while doing laundry and running the dishwasher."

The "traffic calming" you're proposing provides more roadway than subdivision regulations around the country. In that context, it is not a hazard.

I would wager that any accidents would be due to people driving too fast on the 36' wide speedway that you're trying to calm.

You asked earlier where people would park if not on the street. Well, for a 70' wide lot, they could stack 3 or 4 (or even 5) cars on the street in front (on each side of the street). Presumably there's room on the lot for a double garage and a driveway; how many cars do these people need?

You have a number of valid points and are raising good questions. Fire can handle an isolated choke point since a fire truck will fit within a 12' travel lane. As for where to park, a situation has developed in California that I'm not sure is occurring elsewhere. Due to high housing prices and a lack of affordability (i.e. in many counties, only 15 to 30% of the population can afford the median priced home), many families buy something smaller and then use their whole garage for storage, work-out room, play room, etc. Thus their 2 (or 3 if they have teenagers) cars wind up in the driveway. Thus on-street parking on both sides of the residential street is a standard expectation. Thanks again for the great input - do you have any city websites you could point me to for these lesser subdivision standards?

I think if one observed firefighters in action one would notice that during their process they hurry back and forth alongside the vehicle. 6 feet on either side would seem to be reasonable.

As far as "how many cars do these people need" I think that statement is a succinct summary of a specific attitude with respect to desire to control; certainly in concert with wanting to slow traffic.