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Traffic calming options

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There have been quite a few studies conducted by state and federal agencies that measure and compare the effectiveness of various traffic calming options. As you might have guessed, each has its advantages and disadvantages. The following offers a synopsis of the research findings and will help guide you to the option that is best suited for your situation.

Pro’s: Inexpensive, easy to implement at most locations.Con’s: May actually increase pedestrian danger! Ongoing controversy surrounds the use and effectiveness that marked crosswalks have on pedestrian safety. Many consider them a great tool for slowing traffic and alerting drivers of heavy pedestrian zones. Unfortunately, studies suggest that the opposite might be true. In the most thorough study of it’s kind, the U.S department of transportation analyzed statistics of pedestrian accidents that involved 1000 marked and 1000 similar but unmarked crosswalks in 30 different cities over a five-year period


(1994-1998). All sites in this study had no traffic signal or stop sign on the corner. Data was collected on traffic volume, the number of pedestrians using the crosswalk, the number of lanes, median type, speed limit, and other variables. The study found that on two-lane roads, a marked crosswalk had no effect on reducing pedestrian accidents as compared to unmarked crosswalks. Furthermore, on heavy traffic multilane sites, marked crosswalks were associated with a higher incidents of pedestrian accidents than unmarked crosswalks.


Pro’s: Uncomplicated to install.

Con’s: Not effective in slowing traffic. May cause speeding, noise, pollution and dangerous road conditions.

While both of these options seem logical enough, studies have again shown that the opposite might be closer to the truth. Stop signs are generally used to indicate which driver has the right-of- way at an intersection. They are great at preventing crashes – not so good at getting drivers to reduce speeds. In fact, it’s been found that drivers often increase their speed after stopping at a stop sign. When signs are posted for the purpose of slowing traffic, studies find that drivers often exhibit a resentful attitude toward them. This increases the chance of drivers simply running the stop signs as well as speeding. Not good.

Installing speed limit signs may seem to be a logical solution to remind drivers not to speed. But numerous studies show that speed limit signs have little impact on actual driving speeds! They find that drivers do not operate by the speedometer but by the conditions they meet.

More often then not, they ignore posted speed limit signs and drive at a rate they consider convenient, reasonable and safe under existing conditions. Right or wrong, these findings strongly suggest that speed limit signs have little effect on slowing traffic.

Pro’s: Moderate cost. Effective in slowing speeds. Government familiarity.

Con’s: Increased noise level. May impede fire trucks and on the emergency vehicles. May be unsafe to bicyclers, motorcyclists and others.

Employing speed bumps in order to slow traffic has been a popular choice for neighborhoods and government agencies throughout the U.S. In the past twelve years, the city of Portland, Oregon for instance has installed more than 300 speed bumps. The reaction has been mixed.

While speed bumps are proven effective in slowing average traffic speed, they also have drawbacks that must be considered. The first is noise.

Researchers of one study estimated that the undulation of cars passing over the speed bumps increased the volume of car noise by 10 to 20 decibels. Another test found that cars driving over the bumps at 10-15 mph had a noise level equal to a car traveling 25-30 mph. Trucks passing over the bumps at 5 to 10 mph had a noise level equal to a truck going 25-30 mph. The study also concluded that the slower speed made the noise last over a longer period of time.

As an anecdote, there is a local story circulating around one state in the Midwest about a city official that went to great efforts to have a speed bump placed on the neighborhood street right next to his house. Once completed, he immediately noticed that when an open bed truck drove across the bump, the tools, concrete, equipment and whatever else was being hauled in the back of the truck would fly

in the air and slam back down, creating a noise that was constant and distracting. It took him quite a bit longer to have the bump removed than it did to have it installed.Another concern with speed bumps is that they impede fire trucks and other emergency vehicles. For this and other reason, city traffic departments typically conduct extensive evaluations of the target sites before improving installation. Speed bumps are usually prohibited on streets designated as main routes for emergency vehicles.One last consideration is the fact that speed bumps, like stop signs, often have a negative effect on adjacent streets. Drivers will often change their driving pattern to avoid the bumps all together which simply moves the problem from one block to the next. For this reason, you may find nearby neighbors opposed to any plans for installing speed bumps.

Pro’s: Moderate cost. May be effective at low speeds.

Con’s: Increased noise level. May be hazardous to bicyclists.

Rumble strips have been used primarily to alert drivers to upcoming stop signs or other traffic signals ahead. Studies of their use for calming traffic are limited – particularly at slower speeds where the discomfort that they produce tends to be milder than at higher speeds. The studies that have been done seem to indicate that rumble strips may cause drivers to slow down.

In one study conducted in San Francisco, the rumble strips reduced speeds from 5 to 15 mph for cars traveling at speeds of 16 to 30 mph. In a study done in Canada, the rumble strips appeared to have the effect of reducing average traffic speeds by 1 to 4 mph with cars traveling approximately 21-28 mph.

The biggest concern with rumble strips is the noise they produce. The studies conducted in the U.S. only tested the noise level inside the car (with closed windows) but found the bumps raised noise levels from 92 to 100

decibels. Other studies produced similar, yet less dramatic results. In several Canadian studies, the rumble strips were eventually removed due to neighborhood complaints regarding the increased noise level they produce.

Pro’s: Moderate cost. Highly effective in slowing traffic. Mobile.

Con’s: Requires power (DC or solar).

They are called radar speed signs, speed reader boards, driver feedback signs and “Your Speed” signs. They can be permanently mounted like any other traffic sign or they can be attached to a trailer and moved from one location to another. All speed reader boards tell drivers their actual speed as they pass by. Some flash warnings when speeds reach a pre-set limit.

The studies done on driver feedback signs indicate that they are highly effective in slowing traffic, particularly when used on residential streets, near school zones and around playgrounds. They have greatest effect on those who are traveling significantly over the speed limit. Interestingly, research results also indicate that these traffic calming devices have a long-lasting effect. They continue to calm traffic even after they become long-standing fixtures at a location. A study conducted by the Texas Transportation Institute showed that almost the same speed reduction was being achieved four months after installation. Other studies have shown drivers exhibit traveling significantly reduced speeds even months after the sign are removed. In a recent survey, traffic engineers and other safety professionals ranked driver feedback signs as the most effective traffic calming method for neighborhoods and school zones. Researchers suggest that the sign’s effectiveness is due to the fact that, unlike static speed signs that are often ignored, feedback signs refocus driver attention on their own speed rather than on their personal evaluation of driving conditions.


Radar speed signs do require power to operate. Some are designed with batteries that require ongoing recharging. Solar powered signs are also available.In an effort to help neighborhoods reduce speed problems, the Portland Bureau of Transportation System Management (BTSM) has just launched a Neighborhood Speed Reader Board Deployment Project. Under this program, BTSM will maintain a limited pool of driver feedback signs that can be temporarily deployed upon the request of concerned has also developed a national program with a goal of making more driver feedback signs available to local neighborhoods and organizations..

There are other traffic calming strategies that have been employed in cities across the country. They typically include more dramatic changes to street design and other major construction considerations. You can learn

more about these options at a variety of web sites. One particularly useful site is that includes an on-line library of information. The site is a collaborative effort between the Institute of Traffic Engineers (ITE) and the Federal Highway Administration.
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Lightcast offers : many versions newly designed oem and retail products for forklifts, carts, trucks, automobiles, campus, city, county, neighborhoods,manufacturing facilities and warehouses. We design and offer many versions of radar signs, radar speed signs, radar speed monitors, radar speed displays, radar speed trailers, radar trailers, speed monitors, driver feedback signs, radar monitors, solar speed signs, radar speed display units, mobile dolly radar sign, photo lidar, traffic calming devices, traffic calming signs, VSL Signs (Variable Speed Limit signs), radar speed feedback sign, MUTCD signs, changeable message signs boards, work zones signs variable message signs boards, work zone safety signs, Vehicle Speed Feedback Signs, Radar Speed Limit (R2-1) signs, signs in temporary traffic control zones, electronic speed display signs, vehicle activated sign (VAS). We also offer radar speed cameras, hard to find low speed radar, photo enforcement cameras, speed cameras, radar video, traffic cameras, parking lot deck video speed cameras, breathalyzers, breathalizers, alcohol testers, CMI intoxilyzers, breath testers, video analytics and videomanagement systems for traffic and speed control. Call and ask if we can build it for you.

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