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If you haven't
already done so, please read the Expanded version
of Defect # 2.
Defining "Approach
Speed"
- history, 1996 - 2006 -
Early
History of the Table
From 1996 until 2002,
the Yellow Change Interval table published in the main portion of
the Traffic Manual was in increments of 5 kilometers per hour. While
the "metric" version of the table had been
revised/obsoleted by a memo issued April 1998
(available
online, in a Manual section called "New Policy"),
until November 2002 the obsolete metric table
remained in the main portion of the official
electronic edition of the Manual, often confusing
viewers who did not know it was necessary to check
for revisions.
The obsolete
("metric") table is no longer available on the CalTrans
website. Here is a copy of it, from my files:
(for a larger copy, click on the image)
Click on image above for
a larger copy of the obsolete ("metric") table.
In 2002 the
California State Auditor wrote:
"From the survey, traffic engineers
determine the maximum speed that 85 percent of the
motorists are traveling - commonly referred to as the
85th percentile - and compare it to the posted
speed. Often a speed survey shows that most
traffic is driving faster than the posted speed.
In these circumstances, the chief [ of the CalTrans
office of Electrical Systems ] stated, traffic
engineers should use the higher speed for determining
the minimum yellow light interval."
(California State Auditor's report, page 40 - see Links
page.)
The Auditor also
recommended:
"To avoid the
risk of legal challenges, local governments should
petition CalTrans to clarify its traffic manual to
explain when local governments should use either
posted speeds or the results from speed surveys to
establish yellow light time intervals at intersections
equipped with red light cameras."
(California State Auditor's report, page 46 - see Links
page.)
A 2003 Federal Highway
Administration / Institute of Transportation Engineers
"Informational
Report" recommended:
"If available,
the 85th percentile speed should be used as the
approach speed in this equation. In the absence
of 85th percentile speed, some jurisdictions use
posted speed as the approach speed. In most
cases, using the 85th percentile speed will produce
intervals that are more conservative (i.e., longer).
In no case should the approach speed used in the
calculation be less than the posted speed limit."
("Making Intersections Safer: A Toolbox of
Engineering Countermeasures to Reduce Red-Light
Running," FHA / ITE, 2003, Chap. 3.)
Action in 2004
From the minutes
of the Aug. 12, 2004 meeting of the California
Traffic
Control
Devices
Committee.
Notes added by highwayrobbery.net appear in double
square brackets [[ ]].
8-12-04 Minutes.
04-B Yellow Change Intervals
Timing for the Signals
Chairman Fisher [[ employee, City of LA ]] asked
Committee Member Hamid Bahadori to address the
agenda item of yellow change interval timing for
signals.
Hamid Bahadori [[ employee,
Auto Club of So. Cal ]] noted that the yellow
change interval timing issue needs immediate
attention and clear policy direction from the
CTCDC, especially in light of the increasing
number of automated red-light cameras being used
to enforce red light violations at signalized
intersections. Agencies are using different
methodologies to determine the yellow timing.
Since there is no definition for the approach
speed in the Traffic Manual, or now in the
California Supplement, the issue is what is the
approach speed. Is it a posted speed limit or it
is an 85-percentile speed? When a motorist
receives a citation, the citation does not hold
up in the court because approach speed has not
been defined. The red light cameras are issuing
tickets on a differential of one tenth of a
second. People are challenging red light
violations based on the lack of definition of
approach speed. The law can be defended if there
is a definition for the approach speed and
minimum yellow timing for the left turn
movements. Hamid referred to the State of
Arizona DOT. They have a more detailed policy in
regards to yellow timing for the through
movement and for left turn movements. Hamid
stated that the following two questions need to
be addressed:
? Clarification on what is
the approach speed.
? Should the same speed be used for all
movements, if not, then does policy need to be
established for the left turns approach?
The following Section of the California Vehicle
Code (CVC) requires yellow timing at signalized
intersections where such automated systems are
used, to be established according to the Traffic
Manual (now the California Supplement).
21455.7. (a) At an intersection at which there
is an automated enforcement system in operation,
the minimum yellow light change interval shall
be established in accordance with the Traffic
Manual of the Department of Transportation.
Gerry Meis [[ employee, CalTrans ]]stated that
there is draft language in the agenda packet
which addresses the approach speed issue.
However, it does not address the left-turn
movement yellow timing. This is only a draft,
any suggestions and recommendations will be
considered. Gerry agreed that due to red-light
camera enforcement and that the CVC says the
yellow interval shall be established in
accordance with the Traffic Manual, this section
needs improvement. He welcomed any suggestions
for the improvement of the section. Gerry
inquired, if a major change is recommenced to
the Section, is there a need to change existing
law?
Chairman Fisher stated that
there is a need to clarify left-turn and
right-turn yellow intervals. He also suggested
flexibility so that a local agency can give more
yellow time if it is needed. He added that the
yellow interval should be based on the 85%
percentile speed. The posted speed limit
sometimes is not consistent with the 85
percentile due to political influence. If the
posted speed is not consistent with the 85
percentile, then there will be a problem and
more motorists may pass through the red light.
It could also be a safety problem.
Hamid added that the Traffic
Manual allows the use of the posted speed limit
to determine the location of advance loops at
signalized intersections.
Chairman Fisher invited the
audience to give input.
Ahmad Rastegarpour, Caltrans
Headquarters Office of ITS Development &
Support, stated he believes that in determining
the minimum yellow timing for a signalized
intersection, appropriate judgment must be
exercised. That judgment would be based upon
numerous factors, including the posted speed,
the 85th percentile speed (if available), the
intersection geometrics, the traffic volumes,
through and left turn movements, and other
factors that would not be readily apparent to
motorists using the intersection. To determine
the yellow timing for the left-turn pocket,
there is no guidance available. Therefore, a
field review is needed to determine the left
turns yellow timing which will be based on
geometrics, left-turn pocket, the number of left
turn lanes and other factors. He does not
recommend a minimum yellow timing be set which
would prohibit practitioners from adjustment
based on field conditions.
Hamid commented that he was
also not in favor of putting limitations on the
flexibility for practitioners. However, since
the red-light enforcement, vendors may be
manipulating yellow timing to issue more red
light violations. And since the approach speed
is not defined, they are using their own
criteria for the yellow timing. Secondly, the
courts are throwing violations out because the
approach speed not being defined.
Gerry Meis stated that the
Department would consider all suggestions from
the Committee and work with the Committee to
resolve this issue. He said he was not in favor
of going back to the legislature to amend the
law. Marianne Milligan, City Attorney’s Office
of Costa Mesa, stated that when a City adopts a
document by reference such as the Caltrans
Traffic Manual, the City also adopts later
amendments. She commented that she does not
believe that changes in the Caltrans Traffic
Manual would require action by the legislature.
George Allen [[ employee,
City of Garden Grove ]] commented that for years
their jurisdiction used 3 seconds for the
left-turn lane and 4 seconds for the through
movements. Since the introduction of red-light
cameras, the 85-percentile speed has been used
to determine the yellow timing. The
85-percentile speed was measured between the
advance loop and the limit line. The 85-
percentile speed was used to determine the
yellow timing for the left-turn and the through
traffic. In his opinion, there should be 3.2
seconds minimum for the left turns and use the
table for the through movement. George added
that there is a need to define the approach
speed. If all agencies are using the same
definition then everyone is consistent.
There was a lengthy
discussion regarding the approach speed
definition and the minimum yellow timing for
left turns.
Hamid cited a example where
if a roadway has an approach speed of 40 mph,
and an agency uses a 3 second minimum yellow
timing for the left turn, then a citation will
not hold up in court, because there is no
separate guideline for the determination of
yellow timing for the left-turns. The Traffic
Manual says that the minimum yellow timing is
based on the approach speed, so it applies to
both through and left turn movements.
Marianne stated that local
agencies could defend their case if the
definition of approach speed is clear. It could
be an 85 percentile or posted speed limit.
Approach speed must be clarified. If the
Committee suggests that the left turn must use a
minimum of 3.2 seconds, then all agencies will
be consistent, especially when red-light cameras
are used.
Farhad Mansourian suggested
that this is a discussion item and regardless of
what is done here today, the Committee cannot
take action. He suggested forming a subcommittee
to work on this and bring draft language for the
Committee’s consideration during the next
meeting.
Chairman Fisher established a
subcommittee chaired by Hamid Bahadori [[
employee, Auto Club of So. Cal. ]] with the
members being Farhad Mansourian [[ employee,
County of Marin ]] , Mark Greenwood [[ employee,
City of Palm Desert ]] and Gerry Meis from the
CTCDC. Two outside members, Marianne Milligan,
City of Costa Mesa and George Allen, City of
Garden Grove, were asked to provide input. The
subcommittee was asked to develop draft language
for the next CTCDC meeting.
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The subcommittee wrote a report which
was heard at the Committee's Dec. 8,
2004 meeting. A copy of the report
was included in the agenda for that meeting, at
pages 6 - 18.
The
minutes
of
the
Dec.
8 meeting became available on
the Committee's site, on February 2,
2005. I have been told that the
Committee debated the matter for three
hours. The final vote was 6 - 2
(noes: the CHP and CalTrans
representatives) to adopt the approach
reflected in the Draft, below. Four of
the "yes" votes came from
representatives from two cities having
red light cameras, and two representatives
from the northern and southern California AAA
automobile clubs. There was also a vote
on a motion to set the minimum for a left-turn
yellow at 3.0 seconds. That vote
initially was 5 - 2, then 7 - 0. The
Dec. 8 minutes indicate that Mr. Meis of
CalTrans was one of the (initial) "no" votes,
but do not reflect who the other was. I
made an inquiry to Committee staff, which said
that the other "no" was CHP Capt. Duncan, and
that Mr. Lem [[ employee, Cal. State
Auto. Assn., AAA ]] had left and did not
vote. The minutes also noted that a
minimum of six votes were required for passage
of a motion - meaning that if some of the reps
from the auto clubs and the red light cities
had been removed because of conflict of
interest, neither motion could have passed!
On
Friday
Dec. 17 the following Draft was emailed to
Committee members, along with a request that
they submit their comments by Dec. 21.
That deadline was later extended to Dec. 27.
Draft For Discussion Only
Section
4D.10 Yellow Change and red
Clearance Intervals
Support:
The
purpose
of the yellow signal indication is to warn
traffic approaching a traffic signal that the
related green movement is ending or that a red
indication will be exhibited immediately
thereafter and traffic will be required to stop
when the red signal is exhibited.
Standard:
The minimum yellow
light change interval shall be in accordance
with Table 4D-102. The
posted speed limit, or the prima facie speed
limit established by the California Vehicle Code
(CVC) shall be used for determination of the
minimum yellow change interval for the through
traffic movement.
The minimum yellow
light change interval for a protected
left-turn/right-turn phase shall be 3.0 seconds.
Option:
The minimum yellow light
change interval time for the through movement
and the protected left-turn/right-turn may be
increased based on a field review or by using
appropriate judgment. That
judgment may be based on numerous factors,
including, but not limited to, posted speed,
85th percentile speed, intersection
geometry and traffic volumes.
Table
4D-102 Minimum Yellow Light Change Interval
POSTED SPEED
OR
PRIMA FACIE SPEED
|
MINIMUM
YELLOW INTERVAL
|
mph
|
km/hr
|
Seconds
|
25 or less
|
40 or less
|
3.0
|
30
|
48
|
3.2
|
35
|
56
|
3.6
|
40
|
64
|
3.9
|
45
|
72
|
4.3
|
50
|
80
|
4.7
|
55
|
89
|
5.0
|
60
|
97
|
5.4
|
65
|
105
|
5.8
|
|
Jan. 2005 Official Action Eliminates Use of Term
"Approach Speed"
On
Jan. 26, 2005 the Committee officially changed the
"yellow interval" table (see Defect # 2 on the Home
page) to refer to Posted Speed instead of Approach
Speed. Their decision to use Posted Speed was
at odds with both the CVC 21455.7 reference to
"designated approach speeds" as well as with the
Federal Highway Administration recommendations.
See http://www.dot.ca.gov/hq/traffops/signtech/signdel/policy/05-01.pdf
for the new table, and some background.
The change was published
on Jan. 26, 2005, at http://www.dot.ca.gov/hq/traffops/signtech/signdel/policy/05-01.pdf .
The published Policy
Directive contained a recommendation for a review after
one year, so I sent out the following letter.
11-25-05
From
(highwayrobbery.net)
To Mr. Will
Kempton, Director, CalTrans, (916) 654-5266 fax
(916) 654-6608
Dear Director
Kempton:
A year ago the
California Traffic Control Devices Committee
discussed, and later adopted, a policy that
effectively shortened the minimum length of
yellow time on traffic signals equipped with red
light cameras.
That policy, later
published as Traffic Operations Policy Directive
05-01 of January 26, 2005, included a
recommendation by the Committee that there be a
review after a year. That
year now being about up, I expect that the
policy will be coming under Committee
consideration again, and would like to make the
following observation and request.
Per the minutes of
the December 8, 2004 meeting of the Committee,
there were two votes on the policy. The first vote was 6 -
2, to adopt policy applicable to the length of
yellows for straight-through movements only. In that vote, four of
the aye votes came from Committee members who in
my opinion had a conflict of interest. Two of those four were
employees of cities that operate red light
cameras, and another two were employed by auto
clubs whose main revenue stream comes from the
sales of car insurance. Had
any one of the four voted differently, the
policy would not have passed, as six ayes are
required for passage of a motion.
The second vote,
also during the December 8 meeting, was 7 - 0 to
adopt policy applicable to the length of yellows
for turning movements. Three
of the seven ayes came from members who in my
opinion had a conflict of interest. Had any two of the
three voted differently, the policy would not
have passed. Adding
to the appearance of impropriety, during the
consideration of that policy the committee
requested legal advice from an attorney who was
there representing a city which operates red
light cameras.
I would suggest
that when the policy comes under new review,
that Committee members from cities or companies
which will be directly affected financially be
excluded from the discussion and the voting, and further, that the
Committee obtain its legal advice from a neutral
source.
Sincerely,
|
Here is CalTrans' reply of Dec. 8, signed by Gerry Meis,
Chief, Office of Signs, Markings and Permits:
The One-Year Review
At its Feb. 23, 2006 meeting in Sacramento, the CTCDC
was scheduled to re-evaluate the yellow timing.
(The agenda for the meeting is available on the CTCDC's
site - see link above.)
The meeting did not go well. The committee voted
to not even have a discussion of changing last year's
decision !
The details:
The meeting was on the 23rd, at a CHP building in West
Sacramento.
The item came up just before noon. The chair
announced that the only decision in front of the panel was
whether the matter would be studied and brought back at a
later meeting. (The item was listed on the agenda -
http://www.dot.ca.gov/hq/traffops/signtech/newtech/agenda/Agenda022306.pdf
-
as
"Discussion
item
- Re-evaluation of the decision regarding the yellow light
timing." - and Gerry Meis' short report - at page 28
of the agenda - indicated that during the meeting there
would be a discussion of the length of the yellows.
Had CalTrans rep Meis been present - he was ill - that
discussion might have occurred.)
The chairman also announced that no public input would be
taken, since the item was listed as a discussion item
only. This would have had the effect of
preventing public attendees from addressing the committee
at all, even on the issue of whether the item should be
studied. He made that announcement just before
adjournment for lunch. However, after lunch the
chair said that he had changed his mind and would allow
the public to speak.
All it would have taken was for ONE of the seven members
in attendance to move to have the matter studied and
brought back. Not one of them did so. So,
unless CalTrans decides not to adopt the CTCDC decision to
not revisit the issue (after all, it is just an advisory
committee), yellows in CA will continue to be based on the
posted limit, and with 3.0 seconds minimums on left and
rights.
After the meeting, a public attendee wrote a letter to
Meis, and it is reproduced below, with the author's
permission.
Gerry,
You missed the vote on opening up for review
signal timing standards. The committee voted
to not review current practice. Of course, the
two knowledgeable members of the committee who
voted against this last year were not there -
CHP and Caltrans.
Regardless of the CTCDC, you are the final
safeguard to assure the lives of over 30
million and the million of visitors to the
state are protected.
Best practice are those practices that have
been proven safe. The current practice has
been proven to be inadequate, with negative
consequences for thousands; some die and many
more are injured each year as a result.
Members on the committee took positions to
protect their interest, not the peoples. As
one of strongest proponents of not opening it
up for review said to me privately, we have
too many intersections to do reviews. The same
argument he made to eliminate the requirement
to assure sight distances at intersections and
driveways. Where the majority of the most
serious accidents occur. Again, taking a
position against remedies because you don't
want to do them, is not exactly championing
safe roads.
Someone on the committee has to represent more
than their agency's view, but the peoples best
interests', too.
That leaves you, because as the state traffic
engineer, it is ultimately laid at your
doorstep.
Please do the right thing. The current
practice is not a standard at all, nor does it
contain any checks against deviant practices
either. The 1988 MUTCD section 4b-20 is still
the clearest possible language to assure that
if a defect is discovered, that remedies must
be applied. Turning quantified unsafe
condition, unaltered, into a profit center for
a city... is not a remedy!
The overriding safety emphasis of the
controlling federal traffic safety law is that
"Signal Operations Must Relate to Traffic
Flow" (MUTCD 4B-20). The express provisions of
the MUTCD to accomplish this mandate require
an engineering study as a precondition to
determining the proper phasing and timing of a
traffic control signal, and it shall be
documented. The timing of traffic signals is
determined by an engineering study. The
engineer can either chart how long it takes
traffic to stop after the onset of yellow and
set the signal to meet that need, or use the
ITE kinematic formula; approach velocity
(vehicle speed) is an essential part of that
formula; traffic volume is not a factor in the
formula. Either way, these are only the
starting point of the process. The timing is
to be further adjusted to assure the needs of
the traffic are met.
1988 MUTCD
Section 4B-20: Signal Operation Must Relate
to Traffic Flow
“Traffic
control signals shall be operated in a
manner consistent with traffic requirements.
Data from engineering studies shall be used
to determine the proper phasing and timing
for a signal. Since traffic flows and
patterns change, it is necessary that the
engineering data be updated and re-evaluated
regularly.”
Respectfully,
Chad Dornsife, Director
Best Highway Safety Practices Institute
PMB 193
25 NW 23rd Place, Suite 6
Portland, OR 97210-5599
www.BHSPI.org
|
For the more recent history of the yellow light length,
see the Expanded version of Defect # 2.
If you need information from
CalTrans, call CalTrans headquarters at (916)
654-5266.
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