haven't already done so, please read Defects #'s 2 and 3 on
the Home page
Defining "Approach Speed"
- by Eliminating the Term -
Jan. 2005 Official Action Eliminates Use of Term "Approach Speed"
26, 2005 a CalTrans
committee changed the "yellow interval" table (see Defect # 2 on the
to refer to Posted Speed instead of Approach Speed.
Their decision to use Posted Speed seems to be at odds with both the
CVC 21455.7 reference to "designated approach speeds" as well as with
the Federal Highway Administration
recommendations (fifth paragraph of Defect # 3 on the Home page).
for the new table, and some background.
How the Change Came About
From the minutes
of the Aug. 12, 2004 meeting of the California
Notes added by highwayrobbery.net appear in double square brackets
04-B Yellow Change Intervals Timing
for the Signals
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
? Should the same speed be used for all movements, if not, then does
policy need to be established for the left turns approach?
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
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.
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
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.
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
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.
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.
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
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!
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
purpose of the yellow signal
indication is to warn traffic approaching a traffic signal that the
green movement is ending or that a red indication will be exhibited
thereafter and traffic will be required to stop when the red signal is
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
yellow change interval for the through traffic movement.
light change interval for a
protected left-turn/right-turn phase shall be 3.0 seconds.
yellow light change interval time for the through movement and the
left-turn/right-turn may be increased based on a field review or by
appropriate judgment. That judgment may
be based on numerous factors, including, but not limited to, posted
percentile speed, intersection geometry and traffic volumes.
Table 4D-102 Minimum
Light Change Interval
POSTED SPEED OR
MINIMUM YELLOW INTERVAL
25 or less
40 or less
Needless to say, it got
adopted. It 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.
To Mr. Will Kempton,
Director, CalTrans, (916) 654-5266 fax
Dear Director Kempton:
A year ago the California
Traffic Control Devices Committee
discussed, and later adopted, a policy that effectively shortened the
length of yellow time on traffic signals equipped with red light
That policy, later
published as Traffic Operations Policy
Directive 05-01 of January 26, 2005, included a recommendation by the
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
Per the minutes of the
December 8, 2004 meeting of the
Committee, there were two votes on the policy. The
vote was 6 - 2, to adopt policy applicable
to the length of
yellows for straight-through movements only. In
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
from the sales of car insurance. Had any
one of the four voted differently, the policy would not have passed, as
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
committee requested legal advice from an attorney who was there
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
financially be excluded from the discussion and the voting, and further, that the Committee obtain its
legal advice from a neutral source.
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
the yellow timing.
(The agenda for the meeting is available on the CTCDC's site - see link
The meeting did
not go well. The committee voted to not even have a discussion of
changing last year's decision !
The meeting was on the 23rd, at a CHP building in West
The item came up just before noon. The chair announced that the
decision in front of the panel was whether the matter
would be studied and brought back at a later meeting. (The item
listed on the agenda - http://www.dot.ca.gov/hq/traffops/signtech/newtech/agenda/Agenda022306.pdf
item - Re-evaluation of the decision regarding the
yellow light timing." - and Gerry Meis' short report - at page 28
- indicated that during the meeting there would be a
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,
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.
would have taken was for ONE of the seven members in
attendance to move to have the matter studied and brought back.
one of them did so. So, unless CalTrans decides not to adopt the
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
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.
Please note that despite this big website, I am just one voice among
many. Please contact your State legislators about the Committee,
policy, and the conflicts of interest of its members. When you
contact your legislators, please also ask them to vote 'no' on speeding
ticket cameras or any similar bill - see the Legislation
section on the Action page for more information about current
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.
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.
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
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
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
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!
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.
MUTCD Section 4B-20: Signal Operation Must Relate to Traffic Flow
control signals shall be operated in a manner consistent with traffic
Data from engineering studies shall be used to determine the proper
phasing and timing for a signal. Since traffic flows and patterns
is necessary that the engineering data be updated and re-evaluated
Chad Dornsife, Director
Best Highway Safety Practices Institute
25 NW 23rd Place,
Portland, OR 97210-5599
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.
("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.
2012 Govt. Study Recommends Longer Yellows
In Fall 2012 a government-backed study recommended
substantially longer yellows for thru movements and left turns.
To read more about it, see the Expanded Version of Defect # 3, on this
If you need information from CalTrans, call
CalTrans headquarters at (916) 654-5266.
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