|James W. Sparks, P.E.||August 19, 2002|
Just a short note of concern to the very detailed proposed "accessibility
requirements" being advertised in the Federal Register. Please see to it that
these comments get considered prior to going forward with the proposal.
(1) Input regarding accessibility FROM the accessibility community is essential, and it is good that those efforts are underway.
(2) How those concerns are addressed is an engineering issue as well as an accessibility issue, and any final rules regarding attainment of the issues needs to be processed using the very same procedure all engineering features of that control the public rights of way. While I am sure each proposal is well intended, there are inadvertent SERIOUS consequences that can result from failure to benefit from the years of experience the National Committee on Uniform Traffic Control Devices offers. I can recall an accessibility proposal years ago that would have enlarged signalized intersections by 30% due to a proposal that would set the crosswalks way back from the intersecting streets. Doing so would have adversely affected safety for not only the disabled community but the entire public at large. Fortunately this got resolved.
(3) One current proposal falls victim to the myth that traffic signals are in some way safety devices. THEY ARE NOT. The collision rate at signals is double that of similar unsignalized intersections. Signals are essential (no choice) in some instances, but unless essential are bad medicine and counterproductive to traffic safety. The proposal to have to signalize crosswalks near roundabouts is unwise and counterproductive.
(4) Similarly, the requirement for signalization of right turn lanes is an emotional proposal rather than one conducive to safety of all concerned. To ignore that fact puts all users at risk.
(5) Requiring a specific walking speed other than what has been found to be a good compromise considering all aspects of making signals function safely, is WRONG. There is nothing wrong with making such a proposal, but the final decisions should be made by trained engineers familiar with the upsides and downsides of traffic signals.
Thank you for listening.
James W. Sparks, P.E.
October 22, 2002
Good morning again:
Below I have re-included my comments sent to you in August regarding the Access Board proposals. While I know they are offered up as well intended changes, it is clear that some carry with it some adverse unintended consequences for everybody (including the disabled).
When I sent this to you in August you asked for information as to name and address so I will provide it below again and then paste into this message some more specific comments on signal timing. Before the details begin, let me summarize by saying that the wider streets become, the signal engineer loses flexibility on being able to allocate the green time splits to the proper direction of flow. Also when longer clearance times are used (including when nobody is present to benefit from them) it too eats into the flexibility of allowing the signal to match the demands of users. The longer signal cycles become, the less synchronizable the signals get which in turn increases the crash potential for everybody including those with impairments.
No traffic engineer wants to slight the needs of the impaired in any way, but the traffic engineers are accountable to the public trust to provide as efficient of operation for everybody as they can. Doing so is not only important to safety, but other global goals as well (air quality, energy conservation etc.). What the engineers and Access Board folks need to do is to work together with a myriad of ideas that would help accomplish the goals of everybody. For example, fortunately and because people have common sense, older drivers choose to drive slower than others. The drivers are responsible and know they have slower reaction times, reduced vision, etc that they can cope just fine but must drive slightly slower to allow their reaction times and vision to "fit" the circumstances. This results in our senior citizens having even a better driving record (crashes per million vehicle miles) than do younger drivers. One area that traffic engineers and the Access Board need to work on is educating our mutual constituents that it is not just the clearance times at signals that provides for time to cross the street. In addition there is the WALK time and sometimes additionaly all-red time (not always). The current clearance time walking speeds used for signal timing are conservative now, but still there are folks we are mutually concerned with who cannot cross in that time. Both the Access Board and traffic engineers should be working together to get the word out to those that want more crossing time to wait and begin their crossing at the beginning of the WALK time rather than entering the street at or after the clearance time has begun. Doing so drops the effective clearance time to even a lower rate than proposed.
Below are additional more detailed comments on signal timing prepared by the Phoenix staff. These comments are submitte in my name:
James W. Sparks
Deputy Street Transportation Director
October 22, 2002
City of Phoenix official comments on the Notice of Availability of Draft
Public Rights-of-way Accessibility Guidelines provided by the United States
Guideline's impact on traffic signal operation:
Pedestrian Signal Phase Timing (1105.3)
Creating a standard pedestrian clearance rate of 3 feet per second would negatively impact the signal engineer's ability to manage traffic signals efficiently. For several reasons the City of Phoenix strongly opposes this change.
On a typical major intersection with a street width of 96 feet per approach our pedestrian clearance times (flashing don't walk, yellow and red) would go from 24 seconds at 4 feet per second to 32 seconds at 3 feet per second. This is a 33 percent increase! Add to that 7 seconds of walk time and you have a minimum phase time of 39 seconds, instead of 31 seconds.
If left turn arrows are added into our intersection with the 96' street width on all four approaches the timing would be as follows:
East/west left-turn arrows: 13 seconds including yellow time.
East/west through: 39 seconds including yellow and red time.
North/south left-turn arrows: 13 seconds including yellow time.
North/south through: 39 seconds including yellow and red time.
This gives us a minimum cycle length of 104 seconds, compared to the 90 second cycle we use in Phoenix. On our grid street system the 90 second cycle provides for the smooth progression of traffic required by State Law; 104 seconds would not. The 3 feet per second pedestrian timing would impact every intersection in Phoenix and many cities across the country as well. The result of this would be more delay for the vehicular traffic, more fuel being consumed, more air pollution, and less ability to manage traffic well.
Perhaps a more flexible policy, like the Phoenix policy, that does not rely on a feet per second requirement, but instead uses a hands-on approach of meeting with citizens and determining what help (if any) they actually need, would be a more reasonable approach. Each situation for ADA can be different and we need to keep this in mind during the engineering process.
Accessible Pedestrian Signal Systems (1102.8, 1106)
Installing audible indicators at all signalized intersections can be confusing to pedestrians. Not all intersections have the same geometry and large-scale installations of such devices would be a detriment to the people they are trying to serve. Also, there would be no method to determine if people were using them in the proper manner. This could potentially put the untrained pedestrian at risk.
The City of Phoenix installs audible devices only upon request by visually impaired individuals. When a request is made, the need is confirmed by a local mobility trainer with confirmation that the individuals requesting the device have the proper mobility skills to utilize it. Then the on-site training is competed. This process for each location ensures success for all parties and has proven successful for many years. Blanket deployment of audible devices would not serve the visually impaired pedestrians and would be a waste of tax dollars. For these reasons Phoenix is strongly opposed to blanket deployment of such devices.
Directional Information and Signs (1106.4)
The City of Phoenix works closely with visual impaired people and mobility trainers to ensure pedestrians have the tools needed at the locations needed to maneuver throughout Phoenix. Phoenix has 922 signalized intersections equipped with over 7,000 signs giving pedestrians street-crossing guidance. Currently signs are standard and meet MUTCD guidelines. Requiring custom signs for each intersection seems like a proactive idea but is not practical. It would take an estimated five years and $1 million to complete such a project. Even if federal funding is provided the City of Phoenix does not recommend blanket deployment of such signs.
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