design of speed humps.. - resource...

DESIGN OF SPEED HUMPS...OR

“THE KINDER, GENTLER SPEED HUMP”

Presented By ’

Edward Cline, P.E. Traffic Engineer

Willdan Associates 12900 Crossroads Parkway South

Industry, CA 91746

at

The 45th California Symposium on Transportation Issues

May 12-I 4,1993

Sponsored By:

University of California Institute of Transportation Studies

and University Extension in Cooperation with

Institute of Transportation Engineers American Public Works Association

California Transportation Foundation

1 a

PREFACE

I would like to preface my comments on the Design of Speed Humps with the following statement:

As a practicing professional traffic engineer in the State of California, I am not an advocate of speed humps. I do not believe they should be necessary on public streets, private streets, or most particularly, in parking lots to control the behavior of reasonable people.

That said, I will go on to my beliefs and position on these “roadway design features.”

I believe there is a certain inevitability associated with speed humps. This opinion is based on two facts. They are:

0 There are over 50 cities in California experimenting with (demonstration projects) or using speed humps on public streets. .

0 The Institute of Transportation Engineers appears to be recognizing them, if not embracing them through a series of draft “Policies and Procedures on the Use of Speed Humps.”

This opinion is reinforced by extensive experiences dealing with the age old “problem” of speed on residential streets. I believe that there is not a public road agency in California (with the possible exception of Caltrans) that has not expended a significant amount of engineering and enforcement resource attempting to solve this “problem.”

This opinion is further reinforced by an examination of the “problem”. The “problem” is a basic conflict of priorities and perceived rights with respect to the use of residential streets.

The first priority (and perceived right) is the residents “right” to peace and quiet and a safe place to live and raise their families. This is a basic “Quality of Life” issue. This expectancy has roots in the statewide residential speed limit of 25 mph.

The second, and obviously competing, priorii is the drivers’ “right” to drive these residential streets at a speed they believe safe. These motorists, for the most part, . sincerely believe that their speeds are in fact reasonable.

-I-

t

This opinion is even further reinforced by the decades of attempts at controlling this “problem” by such conventional traffic control devices as “stop” signs, speed limit signs, roadway delineation, and vigorous law enforcement. These attempts have been largely ineffective according to the before and after studies.

The widespread frustrations suffered by residents, engineers, planners, and policy makers have lead to the imposition of speed humps as the solution of last resort. This statement is evidenced by the decision of those 50 plus public agencies, including such significant and influential agencies as the City of Los Angeles and the County of Los Angeles to experiment or use speed humps on their public streets.

In my opinion, any agency which is considering speed humps on their public streets should follow the process shown below before actually pursuing humps as a speed deterrent on public streets:

0 solicit technical input from the engineering staff; 0 solicit an opinion relative to potential liability from the City Attorney and risk

management staff; and . 0 solicit public input relative to the magnitude of the “problem.”

If the policy makers, after carefully considering the costs and risks of placing speed humps on their streets, elect to embrace the concept of speed humps, they should consider the use of the kinder/gentler hump.

The purpose of this presentation is to bring forward a more responsible approach to the speed hump question. This is the birth of the kinder, gentler hump.

-2-

THE BIRTH OF THE KINDER. GENTLER SPEED HUMP

Aaoura Hills. California

After considerable discussion and debate, the City Council of the City of Agoura Hills directed staff to install a series of speed humps on Rainbow Crest Drive between Rigger Road and Reyes Adobe Drive. This direction came as the result of strenuous efforts by the community to solve the speeding problem on Rainbow Crest Drive. The direction was given over the technical objection of staff. The technical report recommended against such action. The engineering staff dutifully prepared plans and issued a contract to install speed humps on Rainbow Crest per Council’s direction. Rainbow Crest is a 40-foot wide typical residential street with a slight downgrade and very light parking.

In October of 1987, the first series of speed humps were installed on a public street in the City of Agoura Hills. The series of three humps were installed by a paving contractor under inspection by City staff. The specifications called for a 3- inch high hump over 12 feet per the profile used by the City of Thousand Oaks.

For whatever the reason, these humps came in at about 2% inches over 12 feet (6 up and 6 down) rather than the 3 inches specified. My first series of test runs over these humps in a fairly new Buick Park Avenue was---Oh-no, they are not severe enough. I found speeds in the 40 to 45 mph range very comfortable. In fact, my internal guidance system prevented me from driving any faster on the 40-foot wide residential street.

The speed humps became the topic of numerous less-than-complementary comments from the residents who fought long and hard for the humps. The City received several suggestions to either do the humps correctly or nail 2x4’s on them.

My reactioIn to these suggestions was to see what the folks are doing as they drive down Rainbow Crest. My initial obsenfations, confirmed by radar speed measurements, are listed below:

0 Traffic is slower (31 mph 85th percentile) l Motorists do not “hurry up and slow” 0 Very little braking l Drivers are operating responsibly 0 There is no “gutter-running”

-3-

Further data confirmed the “after” speed to be holding steady at 31 mph at the 85th percentile. The average speed was 26 mph. The lo-mile pace was about 21 to 30 mph. Follow-up traffic volume counts found that traffic had not diverted to other routes. The original daily volume of 2,200 vehicles remained unaffected.

A neighborhood survey found that 84 percent of those polled favored the humps. Some favored the humps but wanted them more severe. The survey, incidentally, was conducted over a 90 household area including those 15 or 20 homes directly affected by the project.

When it came time to answer those criticisms regarding the severity of the humps before the City Council, I was unable to quantify any change in the prevailing speed of 31 mph. The “before” data appeared flawed as it reported a 31 mph 85th percentile without the humps. Therefore, I was unable to refute the complaint that the 2%inch hump was useless.

I was able to convince the Council that, in spite of the before speed data showing no impact, I believed the 26 mph average speed and the 31 mph 85th percentile was a significant reduction over what the normal “before” data should have shown had it not been somehow flawed. I was able to draw this conclusion based on hundreds of other similar streets where 85th percentile speeds are closer to 40 mph. I was also able to show that the adjacent section of Rainbow Crest, which did not have speed humps, was experiencing speeds closer to those I believed to be normal.

As a result of the City Council hearing on the matter, agreement was reached on three issues:

0 The 2%inch humps will remain for now.

0 The City will conduct a second demonstration project with speed humps to better quantify their effectiveness.

l A Policy on the use of speed humps will be developed as a result of the second demonstration project.

Grey Rock Road was selected for the second project. Grey Rock is a 40-foot wide residential street constructed with some downgrades of about 6 percent. The street carried between 3,100 and 4,200 vehicles per day. The City had received numerous requests for speed humps on the street.

“Before” speed readings were taken with roadway classifiers at three locations along the selected route. Daily traffic volumes were also available from these readings. The results of these data collections are depicted in Table No. 1.

4

Table No. 1 I “BEFORE” SPEED AND VOLUME DATA

Grey Rock Road - Between Cambridge and Deer-view

Daily Volume 4039 Average Speed 32 mph 85th Percentile 35 mph 10 Mile Pace 26-35 mph Number in Pace 79%

Grey Rock Road - Between Castlehill and Laro (at 5940)




Table No. 2 “BEFORE” AND “AFTER” SPEED AND VOLUME DATA

Grey Rock Road - Between Cambridge and Deerview

Daily Volume Average Speed 85th Percentile 10 Mile Pace Number in Pace

Before After 4039 3967 32 mph 23 mph 35 mph 29 mph

26-35 mph 16-25 mph 79% 64%


Daily Volume Average Speed 85th Percentile 10 Mile Pace Number in Pace

Before 3185 32 mph 38 mph

29-38 mph 70%

After 3252 23 mph 29 mph

17-26 mph 67%


Daily Volume Average Speed 85th Percentile 10 Mile Pace

LNumber in Pace

Before After 3216 3211

29 mph 20 mh 35 mph 29 mph

26-35 mph 16-25 mph 759/o 62%

A series of five (5) speed humps were constructed under contract along the lh mile length of Grey Rock Road. The specifications required a 2%inch hump over 12 feet. Interestingly, only four of the five humps came in within specification. For some reason, one (not at either end) came in closer to 3X inches. It was quickly removed and replaced with the 2%inch variety. Complaints about severity went away just as quickly.

“After” data was gathered about 6 weeks after the installation. Roadway classifiers were used for consistency. The “before” and “after” data is shown on Table No. 2. As you can see, the average, 85th percentile and lo-mile pace dropped, consistently across the project limits. I believed this decrease in prevailing speeds to be significant. Observations indicated that a fairly even speed profile was obtained, that little “hurry up and brake” mentality prevailed and there was no gutter running. Also, there was no diversion of traffic to other residential streets.

A public opinion poll was conducted over 135 households in the area. The acceptability factor was 67 percent. The most common complaint was “the warning signs are ugly.” Interestingly, positive responses were 54 while only 26 homes were directly affected by the project.

Armed with the results of Demonstration Project No. 2 and a fairly high acceptability rating from the community, we returned to the City Council with a recommendation to adopt Policy No. 27 dealing with speed humps in the City of Agoura Hills. Policy No. 27 was adopted on a 5 to 0 vote. A copy of Policy No. 27 is attached.

Since that time, two other speed hump projects have been completed in the City of Agoura Hills. Both of these projects were constructed in accordance with Policy No. 27 using a specified height of 2% inches (plus or minus Mnch) over 12 feet. Spot speed surveys using hand held radar indicate speed reduction in a similar range as the Grey Rock project. The speeds were slightly higher (1 or 2 mph), possibly due to differences between radar observations and roadway classifiers.

The neighboring City of Westlake Village engaged in a speed hump project shortly after Policy No. 27 was adopted in the City of Agoura Hills. A series of seven (7) humps were placed on Three Springs Road north of Triunfo Canyon Road. Their “before” and “after” speed results are depicted in Table No. 3. The Westlake Village humps are constructed in accordance with the 2%-inch (*l/d) specification.

As you can see, the results of the tests on the humps in Westlake Village are very close to the results on Grey Rock Road. The Westlake Village data includes some information that goes beyond our tests in the City of Agoura Hills. First, speed readings were conducted before and after the installation of 25 mph speed limit signs. Second, “after” speed readings were obtained between the humps. Thirdly, maximum speeds were obtained before and after the hump installation. Finally,

-5-

Table No. 3 THREE SPRINGS DRIVE SPEED SURVEY DATA

rHREE SPRINGS DRIVE:A’T’TI-IREE SPRINGS PARK ,..,. . . ..(..,, . . . . . ..A. 50TH 85TH PACE %’ IN PA& MIN

6:30-7:30 AM 3EFORE 25 MPH SIGNS 19 9FTER 25 MPH SIGNS 17 4FTER HUMPS (AT HUMPS) 10 IFTER HUMPS (BETWEEN HUMPS) 16 I YR. LATER, AFTER SLURRY (AT HUMPS) 12 I YR. LATER, AFTER SLURRY (BETWEEN HUMPS) 15

32 31 21 24 22 25

38 36 29 29 26 29

27-36 25-34 15-24 19-28 17-26 21-30

10:00-l 1:OO AM 3EFORE 25 MPH SIGNS 15 4FTER 25 MPH SIGNS 17 4FTER HUMPS (AT HUMPS) 11 9FTER HUMPS (BETWEEN HUMPS) 13 I YR. LATER, AFTER SLURRY (AT HUMPS) 12 I YR. LATER, AFTER SLURRY (BETWEEN HUMPS) 20

31 32 20 23 24 26

36 37 26 29 28 29

25-34 27-36 15-24 20-29 20-29 21-30

4:00-5:00 PM 3EFORE 25 MPH SIGNS 30 9FTER 25 MPH SIGNS 31 9FTER HUMPS (AT HUMPS) 21 4FTER HUMPS (BETWEEN HUMPS) 25 1 YR. LATER, AFTER SLURRY (AT HUMPS) 25 1 YR. LATER, AFTER SLURRY (BETWEEN HUMPS) 27

37 29-38 37 26-35 27 15-24 29 19-28 30 20-29 31 23-32

48 19 45 19 37 11 39 18 43 13 45 17

THREE’ SPRINGS DRIVE NORTH OF ASPENVIEW COURT

7:30-8:30 AM 3EFORE 25 MPH SIGNS 19 AFTER 25 MPH SIGNS 15 AFTER HUMPS (AT HUMPS) 10 AFTER HUMPS (BETWEEN HUMPS) 18 1 YR. LATER, AFTER SLURRY (AT HUMPS) 10 1 YR. LATER, AFTER SLURRY (BETWEEN HUMPS) 14

32 30 21 23 24 26

38 35 24 27 28 30

27-36 25-34 15-24 18-27 19-28 22-31

1:30-2:30 PM BEFORE 25 MPH SIGNS 30 AFTER 25 MPH SIGNS 29 AFTER HUMPS (AT HUMPS) 21 AFTER HUtiPS (BETWEEN HUMPS) 24 1 YR. LATER, AFTER SLURRY (AT HUMPS) 26 1 YR. LATER, AFTER SLURRY (BETWEEN HUMPS) 27

36 25-34 36 27-36 27 14-23 29 20-29 33 21-30 30 22-31

62 71 60 79 78 86

65 67 65 79 77 84

61 68 68 84 71 78

62 70 72 88 77 81

65 69 68 81 58 80

53 76 68 79 87 88

46 15 49 19 38 10 38 17 37 19 40 17

5:00-6:00 PM BEFORE 25 MPH SIGNS AFTER 25 MPH SIGNS AFTER HUMPS (AT HUMPS) AFTER HUMPS (BETWEEN HUMPS) 1 YR. LATER, AFTER SLURRY (AT HUMPS) 7 YR. LATER, AFTER SLURRY (BETWEEN HUMPS)

30 39 29-38 49 19 32 36 27-36 45 19 20 27 16-25 35 10 24 29 20-29 36 15 22 26 18-27 35 17 26 29 22-31 38 20

MAX

50 44 36 39 33 35

46 49 37 37 37 39

50 41 33 35 40 40

speed readings were obtained after about one-year following a coat of slurry being applied to the street and humps.

As you can see, neither time nor slurry caused the results to diminish. As a result of the experiences in the Cities of Agoura Hills and Westlake Village, considerable interest in the 2% (*l/s)-inch hump has been shown by the City of Los Angeles and the County of Los Angeles. The City of Los Angeles has several demonstration projects in place using the 2%-inch humps. They have repotted similar results as were found in the Cities of Agoura Hills and Westlake Village. The County of Los Angeles has recently placed 2%-inch humps on three streets in the Altadena area. The County has not completed its evaluation at the time this paper is being written. I have visited both the City humps and the County humps with the Buick test vehicle and found the comfort level to be similar to that found in the Cities of Agoura Hills and Westlake Village.

In conclusion, I believe it is safe to say that speed humps can be an effective tool in combating the residential speed “problem.” I also believe the 2%-inch solution is far better and a more responsible solution than the more severe humps (3 inches +). I further believe that even a quarter of an inch in height over 12 feet will . create significant change in prevailing speed. Some of the benefits I have seen using the kinder, gentler hump are:

0 Reduced prevailing speeds.

0 Prevailing speeds reasonably close to the residential speed limit.

0 Reduction in the use of engineering resource to solve the “problem” on the streets treated.

0 Reallocation of enforcement resource away from the perceived “problem” toward real situations.

I believe that it could be argued that the less severe hump results in less potential for an accident “caused” by the hump. This would logically reduce potential liability for the agency.

Even the complaints of “ugly signs” have gone away with time. Apparently, the complainants enjoy the improved “quality of life” and are resigned to the need for adequate warning.

On the negative side of the coin, the City of Agoura Hills receives quite a number of requests for speed humps now that the issue of whether or not they will be allowed on public streets has been resolved. Many requests have come from short, low volume streets. We have even had requests for a hump or two on cul- de-sac streets serving only a few homes.

So far, we have been able to say “no” to most of these requests because traffic conditions, namely the minimum volume criteria, has not satisfied all of the provisions of Policy No. 27. So far, the City Council has supported all staff recommendations against speed humps on these low volume streets. I am therefore convinced that a minimum volume criteria is vital to the speed hump program. I am also convinced that the 60 percent petition requirements has had an impact on the number of formal requests received.

One of the most important features of Policy No. 27, in my belief, is the minimum volume of 2,000 vehicles per day. There is no doubt that some speeding occurs on every street, no matter its length or volume of traffic. I am resigned, however, to the fact that we cannot solve every social ill and that the now and then abuse of a typical residential street is something we have to live with as being part of the cost of being in the main stream of society.

I believe, on the other hand, that once traffic builds on a residential street to a point beyond the street’s “environmental capacity,” some remedial measures should be considered. Many in our industry see 2,000 vehicles per day as the “environmental capacity” of a residential street; beyond which the residential . ’ character of the street and thus the “quality of life” is compromised.

Taking this concept further, we should look at the reason the “environmental capacity” of the street has been exceeded. In some cases, the cause may be traced to either an inadequate arterial system or an incomplete arterial network. In other cases, the cause may be directly traced to development practices which relied on the use of the residential street for access to too great of extent.

In any of these cases, it could be argued that agencies have a higher responsibility to its residents when the agencies’ policies and practices have contributed to the “problem.” I believe in these cases, an agency may owe the residential community an “environmental correction” on those streets where the “quality of life” has been compromised by traffic flow.

Consequently, I strongly recommend a reasonable minimum volume criteria to be included with any speed hump policy. After nearly 4 years experience with Policy No. 27 in the City of Agoura Hills, I would not change anything.

Recognizing the inevitability of the use of speed humps as roadway design features on public roadways, here are a few things I would like to see in the future:

0 A drift toward a more responsible and less severe hump; one that reinforces the residential speed limit rather than create speeds well below 20 mph.

0 The use of speed humps as an “environmental correction” rather than a solution to an everyday situation.

-70

.

0 A responsible set of uniform standards for the use of speed humps on public street.

0 A position from the legal profession relative to the undefined and unknown potential liability question.

I recognize that the latter will probably not be forthcoming until some standards are developed and embraced by the engineering community.

I note that more on this topic is going to be presented at the ITE District No. 6 Conference to be held July 11 through 14, 1993, at the Riviera Hotel in Las Vegas. A new set of “Proposed Draft Policies and Procedures” is on the agenda.

Attachment, Policy No. 27

wldn\rpt\ttl41

-8-

.

7 Lr - -

!------I

C-1

7.. -

: :

- ^,

-co b-4 - \

- \

” \

i

- ’

I ,- I

,

POLICY NO. 27 c SPEED BUMPS/HUMPS

Recommended Guidelines for the Installation of 8Deed Hu!D~ cq 0

Speed humps, such as those used in demonstration projects on Rainbow Crest Drive and on Grey Rock Road, may be considered on other residential streets in the City of Agoura Hills, when u of the criteria, as indicated below, are satisfied.

8 Reauests. Requests for speed humps should be supported by written documentation which demonstrates that substantial interest in the roadway design features is present on the specific street being considered. To that end, a petition bearing the name, address and telephone number of at least 60% of the affected residents requesting the humps should be submitted. . .

The City Council is to make the final determination on all speed hump installations.

8 The SD886 RUE@ All speed humps shall consist of deflections in the paved roadway surface that provide for a uniformly varying height to a maximum of 2 5/8*@ + l/8" over a 12 foot long base. The construction, markings and warning of the hump shall comply to current standards developed by the City's Public Works Department.

8 The Street. All streets considered for speed humps shall be a minimum of l/4 mile in length and conform to the definition of "Residence District" in the California Vehicle. Code (Section 515), and qualify for a 25 mph speed limit. All streets should also have a local street functional use. Streets on the City's Circulation Element in the General Plan shall not be considered for speed humps.

The grade of the street should not exceed a sustained grade of 68. Exception for street grades up to 8% may be allowed where the steeper grade prevails over relative short distances. The maximum length of six plus percent grade should be limited to no more than 400 feet. Very short grades of up to 10% could be tolerated. The length of grade in this category should not exceed 200 feet.

8 mm. Speed humps should generally be installed at approximately 400 ft. spacing. If street lighting exists on the street, humps should be installed as close as possible to the lights for maximum illumination. Care

.

sh&ld be taken to avoid driveways and manholes. On curving streets, the humps should be placed at or near tangent sections of roadway. Care should also be taken with regard to visibility over crest vertical curves. The minimum number of humps constructed on any street should be three.

a Traffic volume. Streets should have a minimum daily volume of 2,000 vehicles before humps are considered. This volume of traffic is the level at which the residential character of the street is compromised.

n Traffic SDeeds. A speed survey should demonstrate that 60% of the vehicles on the street are exceeding the 25 mph speed limit. Furthermore, the finding of excessive speed should be made only after attempts at controlling the speed using specialized enforcement has proven ineffective. . .

n prioritisatiog. In the event several requests fox speed humps are pending at any given time, (1) those with the greatest incident of reported accidents involving excessive speed, and (2) those locations with the highest volume of traffic should be given the highest priority.

a pernova& The removal of any hump, or series of humps, should be considered, following the same procedures used to determine the installation.

February 14, 1990

.’ .

PORT TO CITY CcXl’NCX&

To: TERRY S. MATZ CITY MANAGER

FROHt

BY:

VINCE MASTROSIMONE

b IRECTOR OF PUBLIC WORKS/PERSONNEL

ED CLINE TRAFFIC ENGINEER

SUBJECT: SPEED HUMP POLICY

DATE: JANUARY 12, 1994 CONSENT

BACKGROUNQ

At their September 22, 1993 regular meeting, the City Council considered modifications to the City Speed Hump Policy. The modifications were generally directed at the minimum volume criteria.

After considerable discussion, the City Council moved to retain the existing criteria (2,000 vehicles per day) but add additional factors such as:

. Streets that front schools or parks;

. Streets that are a continuation of other streets which currently have speed humps; and

. Lowering the volume requirement if a greater than 60 percent of homeowners feel that humps are needed.

The motion was passed on a 3/l vote.

I have given these factors considerable thought. streets fronting schools and parks,

With respect to

the following conclusions: these thoughts lead staff to

Streets with schools and active parks (those with organized activities) will generally have higher volumes of traffic than residential streets without those traffic generators. However, it is possible that the 240hour volume of 2,000 vehicles will not be satisfied.

Traffic generators such as schools and active parks can, on the other hand, experience peak traffic periods that would, if sustained throughout the day, exceed the minimum 2,000 daily volume. Since the activities which generate traffic have relatively short

122093 CT/SPEEDHUP.WD

RT TO CITY COUNCI& SPEED HUMP POLICY JANUARY 12, 1994 PAGE 2

durations, the 24-hour volume is too low to qualify the street for speed humps. However, the hourly volume may exceed 200 vehicles.

When we examine the rationale behind the 2,000 vehicles per day minimum criteria we find that what is actually felt by residents is the peak travel period. The normal distribution of traffic through out the day would provide peak periods of 200 (10 percent of 240 hour volume). Since it is this hourly volume which is actually felt, an alternative criteria of 200 vehicles per hour, or 2,000 per day would be appropriate and in keeping with the original intent of the criteria.

I believe that modifying the criteria to accept 200 vehicles per hour minimum in lieu of the 2,000 per day would address the issue of the street serving as direct access to schools or parks whether the street actually passed by the attraction, or simply went directly to the school or park.

With respect to offering a "special circumstance" criteria on streets that are logical or actual extensions of streets which already have humps, I offer the following:

There is some wisdom to the notion that a continuation of a street which already has speed humps should receive a "special circumstance" consideration. I agree when the traffic on the street has common origins and destinations. In other words, traffic on one street segment may be found on the other segment with a fairly high degree of consistency. An example of this situation may be Grey Rock Road and Fountainwood Street. Other situations may not fall into the "special circumstance" category. Those would be contin- uous streets which are interrupted by an arterial roadway. The general belief in these situations is that traffic on both street segments do not experience common origins and destinations. In most cases, traffic on the subject street would turn onto the arterial rather than continue onto the extended portion. An example of this situation would be Rainbow Crest Drive east of and west of Reyes Adobe Road.

I believe petitions are valuable in determining the sentiment of any group on almost any issue. The 60% requirement associated with the speed hump policy is intended to illustrate significant interest in the speed hump concept. As I have found in other communi- ties, speed humps are not always well received in the neighborhood.

I further believe that the strength of the petition beyond the point where it is obvious that significant interest is present in

122093 CT/SPEEDHW.I+#

RT TC CITY CCDNCIt SPEED HUMP POLICY JANUARY 12, 1994 PAGE 3

any issue is more a function of the persistence of the petitioner than a higher expression of interest or concern. The fact that a petition contains significantly more than the minimum 602 does not necessarily indicate that traffic conditions are more severe than the traffic study would reflect. In other words, the petition is needed to start the process but the process should dictate the recommendation based on other aspects of the policy.

In order to address the greater severity of the situation, we should rely on the data itself. If, for instance, the speed check information revealed that the prevailing speed (85th percentile) was found to be significantly higher than that which is thought to be Wormal" I a reduction in the minimum volume would be supported.

To that end, we-Gould use criteria from the State Traffic Manual that allows a .iO% reduction in traffic volumes when prevailing speeds exceed 40 MPH when considering multi-way stop controls for traffic signals.

Therefore, I would propose that the threshold volume of 2,000 vehicles per day (or 200 per hour) be reduced to 1,400 per day (or 140 per hour) when observed speeds exceed 40 MPH.

RECOMMENDATIOY

Based on the thought given the circumstances and the consideration outlined above, the following modifications to the City's Policy on Speed Humps (827) are submitted for your consideration:

. Amend the minimum volume criteria to 2,000 vehicles per day or 200 vehicles during any peak hour.

. Allow for "special circumstances w to exist that would justify the installation of speed humps or continuations of streets already containing speed humps which are not interrupted by an arterial route.

. Retain the present 609 petition process without concessions for petitions with significant higher representation from the potentially affected community.

. Amend the minimum volume criteria to provide for a reduction . of 70% (to 1,400 per day or 140 per hour) when the prevailing ' speed (85th percentile) exceeds 40 MPH.

122093 CT/SPEED WP .mO

POLICY NO. 27 SPEED BURPS/HUMPS

(Revised January 12, 1994)

Recommended Guidelines for the Installation of Sneed BWQDS on Public Streets Within the City of Acroura Hills

Speed humps, such as those used in demonstration projects on Rainbow Crest Drive and on Grey Rock Road, may be considered on other residential streets in the City of Agoura Hills, when a of the criteria, as indicated below, are satisfied.

I Juwnsests. Requests for speed humps should be supported by written documentation which demonstrates that substantial interest in the roadway design features is present on the specific street being considered. To that end, a petition bearing the name, address and telephone number of at least 60% of the affected residents requesting the humps should be submitted.

The City Council is to make the final determination on all speed hump installations.

I The SDsed Humu. All speed humps shall consist of deflections in the paved roadway surface that provide for a uniformly varying height to a maximum of 2 5/8" f l/8" over a 12 foot long base. The construction, markings and warning of the hump shall comply to current standards developed by the City's Public Works Department.

I The Street. All streets considered for speed humps ,shall be a minimum of l/4 mile in length and conform to the definition of "Residence District" in the California Vehicle Code (Section 515), and qualify for a 25 mph speed limit. All streets should also have a local street functional use. Streets in the City's Circulation Element in the General Plan shall not be considered for speed humps.

The grade of the street should not exceed a sustained grade of 6%. Exception for street grades up to 8% may be allowed where the steeper grade prevails over relative short distances. The maximum length of six plus percent grade should be limited to no more than 400 feet. Very short grades of up to 10% could be tolerated. The length of grade in this category should not exceed 200 feet.

I The Location. Speed humps should generally be installed at approximately 400 foot spacing. If street lighting exists on the street, humps should be installed as close as possible to the lights for maximum illumination. Care should be taken to avoid driveways and manholes. On

122093 cT/PoLIcYz7.REv

curving streets, the humps should be placed at or near tangent sections of roadway. Care should also be taken with regard to visibility over crest vertical curves. The minimum number of humps constructed on any street should be three.

I Traffia Volume. Streets should have a minimum daily volume of 2,000 vehicles or 200 vehicles per hour during any peak period before humps are considered. This volume of traffic is the level at which the residential character of the street is compromised.

a Traffic! SD88dS. A speed survey should demonstrate that 60% of the vehicles on the street are exceeding the 25mph speed limit. Furthermore, the finding of excessive speed should be made only after attempts at controlling speed using specialized enforcement has proven ineffective. At locations where the prevailing speed (85th percentile) is found to exceed 4Omph, the daily or hourly threshold volume can be reduced by-70%.H, <,

I Bmaial Circumstances. A "special circumstance" can be considered on streets which are an extension of streets which already contain speed humps. The "special circumstance" would not apply to street extensions which are interrupted by an arterial highway.

n prioritization. In the event several requests for speed humps are pending at any given time, (I) those with the greatest incident of reported accidents involving excessive speed; and (2) those locations with the highest volume of traffic should be given the highest priority.

I JZemova&. The removal of any hump, or series of humps, should be considered following the same procedures used to determine the installation.

, 7 * ’ \

. /

.*. ,

Encumbered with a low self-image, Bob takes a jop as a speed bump.

4 ’ *

I INSTITUTE OF

TFkANSPORTATION

STUDIES

Managing Neighborhood _ Tkaffic The growing popularity of speed bumps in California has prompted Traffic Engineer Ed- ward Cline to design a “kinder, gentler speed hump” which he contends reduces the prevailing speed without inducing motorists to“huny- up and slow.”

The “kinder, gentler” hump is about 2’/,-inch high -compared to a height of between 3 and 4 inches for the typical speed hump used in California. Although the difference is small, Cline contends that even a variation of I/, inch is noticeable to drivers who travel over the humps. The installation of one 3’/,-inch-high hump (due toacontractor’s mistake) provoked immediate complaints from irate motorists, Cline says.

The 25/,-inch humps have been tested and accepted for use in the cities of Agoura Hills and Westlake Village. Recently, the city of Los Angeles and Los Angeles County have installed a few 25/,-inch speed humps to see how well they work.

Cline, a consulting traffic engineer for four different California cities and a part-time in- structor on traffic topics, gave his views on the use of speed humps in a skill-building session on neighborhood traffic management presented at this year’s California Symposium on Trans- portation Issues. Also covered in the session were realistic speed zoning and implementa- tion of preferential parking districts.

JULY 1993 - ____..l_-._.___. -_.- _____ -. ._ . : a--_._.~ a_-a..+.- u__ ---

9, c-e, c;&Ts. ;v,, - ‘,, . .

I TECH ,i

! TRANSFER :i ..-_ -_-- --. -- . -. ,. "__. __~__ , . ,;

- _"' , I . . 1 :I i :. f-7 I- -..a.* ia . . . .I L.-r- . - . : .- . '. - ' .z '., ':

;

i> -. - _ .: -. - .,. ---

*," ": 1 ,,' t ._ _/ ,. ,, i

:!.I .i

--.. - . . . - ._. >__ - .-.-. . . .._A :. ,:‘:I ;

-_..

L k-

. ._ ,. . “..*^“._-. __ f -I -‘7 --- 7 1 n Pefia’s Remarks

I

design of speed humps.. - resource...

Documents