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Texas Highway Department

Texas Municipal League

Joint Committee Median Practices on Highway Routes on City Streets

TEXAS HIGHWAY DEPARTMENT TEXAS MUNICIPAL LEAGUE

JOINT COMMITTEE MEDIAN PRACTICES ON HIGHWAY ROUTES ON CITY STREETS

~Austin, Texas "Apri I , 1960

\

TEXAS HIGHWAY DEPARTMENT TEXAS MUNICIPAL LEAGUE

JOINT COMMITTEE MEDIAN PRACTICES ON HIGHWAY ROUTES ON CITY STREETS

Chairman Frank Frey, Urban Engineer, Texas Highway Department ,Austin

Vice Chairman Eugene Maier, Director, Department of Public Works, Houston

Secretary Paul R. Tutt, Supervising Designing Engineer, Texas Highway Department, Austin

Albert W. Rollins George Dieter Lynn Andrews C. J. Griggs Henry B. Nabers· R. W. Burr

C. W. Smith T. C. Collier W. E. Carmichael R. 0. Lytton G. A. Youngs J. F. Snyder

COMMITTEE MEMBERS

TEXAS MUNICIPAL LEAGUE

City Engineer Director of Public Works

City Manager City Manager City Manager

Director of Planning and Traffic

City of Arlington City of Waco City of San Antonio City of Wichita Fa lis City· of Abilene City of Lubbock

TEXAS HIGHWAY DEPARTMENT

District Engineer District Engineer District Engineer District Engineer District Engineer District Engineer

District 4 District 9 District 12 District 15 District 19 District 21

The following people have served on the committee during the course of its work:

F. M. Davis ~ormer District Engineer, Texas Highway Department, San Antonio Marvin Springf'r former Director of the Department of City Planning at Dallas Dick G. Pepin former City Manager at Odessa Drahn Jones former Director of Public Works a+ Corpus Christi Charles Spivey former Director of Planning at Lubbock.

Charles J. Keese, Charles Pinnell, Charley Wootan and others of the Texas Transportation Institute at Texas A and M College assisted the Committee in much of its work.

In addition to these, many of the Districts and Divisions, particularly the Planning Survey Division of the Texas Highway Department and many of the cities of Texas, have assisted the Committee in its work.

STEPHEN J. MATTHEWS Exrndwe D1rcctor

C. C. CRUTCHFIELD Fu·ld Crmsullant

WM. A.. OLSON ],rgnl Coumd

TEXAS MUNICIPAL LEAGUE An Association of Cities for Municipal Progress

TO TEXAS CITIES AND TOWNS

402 Vaughn Building Austin r, Texas GReenwood 6-6oo:;

During the past year and a half,the Texas Municipal League and the Texas Highway

Department have joined in a comprehensive study of practices on median dividers on high-

way routes through our cities and towns. It is noteworthy that it could be done at this

particular time when urbanization- and even metropolitanization- is so rampant, and

traffic problems are becoming more acute.

The League, through its representatives, endorses the findings set out in this report

and encourages all Texas cities and towns to follow the recommendations herein.

We are gratefu I to the League committee members for giving so generously of their

time and talents, and are appreciative of the Texas Highway Department and its staff for

providing the opportunity to study this important area. We trust that the success of this

report and the application of its recommendations will continue the cooperative spirit in

which many mutual problems have been solved.

~ Executive Director

Official Publication TEXAS TOWN & CITY • Member of the American Municipal Association

TO THE HIGHWAY COMMISSION

This report on median practices on highway routes on city streets is unusua I in that

it is the result of efforts of a joint committee composed of representatives of the Texas

Municipal League and the Texas Highway Department. The use of median dividers has been

a worrisome problem to both the Department and Texas cities. This committee was formed

in September, 1958 and has been studying and discussing this matter for more than eighteen

months.

I believe it is significant that a committee of this composition is in agreement. The

cooperatiol") of the League and the time and efforts contributed by the individual members

from the various cities are appreciated.

I endorse the findings set out in this report and believe it will furnish valuable

guidance to both Department and City personnel. The Department is publishing the report

and distribution will be made by both agencies.

D. C. Greer State Highway Engineer

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TEXAS HIGHWAY DEPARTMENT TEXAS MUNICIPAL LEAGUE

JOINT COMMITIEE MEDIAN PRACTICES ON HIGHWAY ROUTES ON CITY STREETS

Mr. S. J. Matthews Executive Director Texas Municipal League 402 Vaughn But I ding Austin, Texas

Mr. D. C. Greer State Highway Engineer State Highway Building Austin, Texas

Gentlemen:

This Committee was formed in September of 1958 through the joint efforts of the Texas Municipal League and the Texas Highway Department. We were asked to s~udy the use of median dividers on urban arteria I routes, these having been a source of some difference of opinion among the various governmental agencies and individua I citizens affected by them in various ways.

The Committee has made a detailed study of this subject and this report represents our findings and recommendations. Additional research Is still in progress and we feel that it should be continued. It is our belief that it will further substantiate the findings presented in this report.

This report is submitted in the hope that you will endorse it and that It will be given wide distribution to City and Highway Department personnel who will be able to use it In the planning and design of urban highway and street work.

Sincerely yours

WHY WAS THE COMMITTEE FORMED ?

General Feobler:r.J.. Statement

To study and make recommendations regarding design policies for medians

on highways in urban areas.

Specific Statement of the Problem

Since the application and design of medians on State Highway extensions

in urban areas is often a matter of controversy among the Texas Highway

Department1 local city officials and abutting businesses 1 it is desirable to

study the influence of median location and design on the safety and capa­

city of an urban highway extension and the economic effect of medians on

abutting business and property owners. The results of the study would be

submitted by this committee to the State Highway Engineer and the Execu­

tive Director of the Texas Municipal League with the recommendation that

theybe adopted for use on highways in urban areas and other urban arterial

streets.

"'\.7\That Is a Median ?

For the purpose of the work of the committee 1 a median is defined as any

traffic separator on a four or more lane road which is more positive than

the standard double stripe at standard spacing.

Classifications of Medians are tabulated on Page 19.

6

WHEN TO USE A MEDIAN

Over a period of time, median dividers have been constructed on numerous urban

arterial projects. Many agencies have been involved and little or no uniformity in the

design and application of medians has resulted. The following are \7\Tarran ts

intended to help standardize the use of medians. When these conditions exist in the design

of a new arterial street or when an existing arterial street is to be improved, a median

which forms a barrier that traffic will not cross intentionally should be included as a part

of the design.

1. The average daily traffic for the design year (usually 20 years in the future) is

9, 000 cars or more, regardless of the expected speeds; or

2. (a) Traffic volumes are su~h that a facility with four or more lanes are needed

for moving traffic. This determination based on the design standards of the

agency responsible for the development; and

(b) The speed which traffic is expected to move during the off:-peak periods is •

35 miles per hour or higher (speed determination should be based on design

operating speed values rather than posted values).

These conditions require a median wide enough to accommodate a lane for left

turning traffic at intersections.

There may be locations where these co11ditions are not satisfied but where a

median is desirable. These locations might be where there are a large number of points of

access to the artery, where it is necessary to control unsafe movements, where a large

number of pedestrians must cross the thoroughfare, where cross street traffic volumes are

unusually high or where one or more other undesirable conditions which might be cured or

partially cured by a median exist . These loc11tions should be studied carefully to deter-

mine if a median would materially improve the situation.

7

~:~~~=--:". - - -----~- - ----

RESUME ~

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FINDINGS & CONCLUSIONS /,/ ~ .

Change has been the byword of our nation's street and highway traffic

since the artificially created period of abatement during the World War 11. Our popula-

tion has Increased. People have moved from the rural communities to the cities. Many of

our cities have more than doubled in population and now cover many times the area which

they formerly occupied. Our automobile population in Texas is now more than three times

what It was in 1945.

These figures have been recounted many times in the past few years and it Is not

necessary to elaborate on them in thIs report. They do make one point very clear ,howeve&

The traffic problem now is not the traffic problem of 1945 and the methods of dealing with

this problem now are not the same methods that would have been satisfactory in 1945.

Dividing the street or highway so that the two opposing streams of moving vehicles

are separated from each other by an area now commonly called a Median has been

found to be one measure which, along with others, will assist in keeping traffic moving in

an orderly, efficient and safe manner. Like many of the measures necessary to keep traffic

moving,the median restricts some traffic movements, thereby causing indirection for some

traffic,but some restrictions are often a matter of public necessity. Owners and occupants

of property adjacent to it sometimes feel that a divided roadway is a detriment to the use

of their property, but, generally, the other improvements and increased traffic efficiency

which accompany the median more than offset any disadvantage, particularly to retail

business.

8

WHY PROVIDE A MEDIAN ? .

The median by itself is not a complete solution to the problem but, when properly

designed and used in conjunction with other improvements,lt can be expected to accom-

plish the following results:

1. The median provides an insulating area between opposing streams of moving

traffic which reduces the strain on drivers and usually results in a reduction in

the accident rate and particularly a reduction in head-on collisions.

2. The median provides protection and control of cross and turning traffic.

3. The median provides a refuge for pedestrians making it safer for them to cross a

a. wide street.

4. The median encourages efficient signing and signalization. More efficient

signing and signalization are possible when traffic movements are regulated

into orderly channels by the median and by other channelizing islands.

5. The median provides space for left turn storage at intersections. At inter-

sections the median should be wide enough to accommodate an added lane for

storing left turning vehicles. This left turn storage lane is one of the most

important benefits of a median. When such a lane is provided, the efficiency

and safety of the intersection is greatly improved. Left turning cars are sepa-

rated from straight through traffic so that they do not impede the flow of the

through traffic, thus increasing the capacity of the street. Also,vehicles wait-

ing to make a left turn are not in the path of the through traffic and are not

likely to be hit from the rear.

6. The median makes it possible for traffic to move smoothly and safely at higher

operating speeds.

9

1. The median provides ·an insulating area between opposing streams of moving

traffic which reduces the strain on drivers and usually results in a reduction in

the accident rate and particularly a reduction In head-on collisions.

10

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2. The median provides protection and control of cross and turning traffic.

11

3. The median provides a refuge for pedestrians making it safer for them to cross a

wfde street.

-----

12

4. The median encourages efficient signing and signalization. More efficient

signing and signalization are possible when traffic movements are regulated

into orderly channels by the median and by other channelizing islands.

13

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STUDY 3-1

-85%-24MPH

85%-24M.P.H.-TYPICAL EXAMPLE

OF WIDE MEDIAN INTERSECTION

WITH TURNING LANES

5. The median provides space for left turn storage at intersections. At Inter-

sections the median should be wide enough to accommodate an added lane for

storing left turning vehicles. This left turn storage lane is one of the most

important benefits of a median. When such a lane is provided, the efficiency

and safety of the intersection is greatly improved. Left turning cars are sepa-

rated from straight through traffic so that they do not Impede the flow of the

through traffic, thus increasing the capacity of the street. Also vehicles wait-

ing to make a left turn are not in the path of the through traffic and are not

likely to be hit from the rear. 14

6. The median makes it possible for traffic to move smoothly and safety at higher

operating speeds.

15

More Facts Spacing of Crossovers

In general, the median should have openings or crossovers at cross street inter-

sections. Where the space between cross streets is very long, it may be necessary to provide

intermediate openings. These should be spaced equally between cross streets to provide

equal service to adjacent property. These intermediate crossovers should not result in a

spacing of less than 360' between openings. Additional openings should not be permitted

for private or business entrances or exits. If these were permitted, the value of the median

would be seriously impared, permitting traffic movements which cannot be accommodated

in an orderly manner and reducing the safety and efficiency of the streets.

Medians on Existing Streets

When a road or street is being constructed on new location or when additional

right of way is being secured to expand an existing thoroughfare, the principles set forth in

this report should be followed. When the traffic demand is such that an improvement must

be made on an existing street on which sufficient right of way cannot be secured, it may be

necessary to accept a design which is an improvement but which is not as good as is need­

ed. When this condition exist~ every effort should be made to provide the added left turn

lane at intersections. It may be possible to do this by eliminating parking for some dis­

tance in advance of the intersection. It should be kept in mind by a II governmenta I

agencies and by all individuals involved that the alternative to improving an existing

thoroughfare to the point where it will satisfactorily accommodate traffic is usually the

construction of another facility on a new location. By improving the existing facility to

its maximum capabilities,the necessity for relocation will be delayed as long as possible.

It is also usually possible to expand the existing facility cheaper and more quickly than it

would be to develop a new location.

16

About Medians Non -Barrier Medians

In those cases where it is not possible, due to limited right of way or other con-

siderations, to construct the type of median recommended, it may be that a median of lesser

design should be considered. Median areas which are formed of a pavement which contrasts

in color and texture with the traveled lane but which do not provide a physical barrier

have been used with good results, and a low blister of asphalt may be suitable for some

situations. This type treatment is not recommended where the warrants for a barrier type

median are satisfied but it is recognized that there wi II be cases where a barrier median is

not practical. It is also possible that a non-barrier median would work well on traffic

arteries where volumes do not require a barrier median under the warrants set forth.

Regardless of the type of median used, the provision of left turn lanes at intersections is

very important.

Transition - Median to Non- Median Section

The transition from a pavement without a median to one with a median, particular-

ly the transition from a rural high speed two lane road to a divided road,has been found to

be an accident problem location in many instances. This part of the design should be

given careful consid!'lrations. If possible, the median should be introduced on the left

side of the approaching traffic in such a manner that approaching traffic is not required to

change direction unti I it is beside the median. It can then be guided into a curved tran­

sition by the median.

- - - - -...... -

~ - - - - - -I Not to Scale I

17

THE WORK /

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O~)HE COMMITTEE--------

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The committee first conducted a rather intensive study of available information on

the subject of medians. A survey of the practices and policies of other States and Cities

was made. Much data were available but little was of a factual nature of the type needed

to establish a sound basis for design. This led to the development of two types of research.

The committee, with the aid of the Texas Transportation lnstltute,began an inventory

of medians in use in Texas at this time. This inventory included approximately sixty

median locations, each about one mile in length. The anlaysis of these studies provided

the committee with much of the factual data needed.

The second type of research was the Initiation of three very detailed "before" and

"after" studies on current median projects. The "before" studies on these have been com-

pleted but as yet the "after" studies have not been made due to the time required for con-

struction of the projects. These each included complete traffic and economic studies. The

committee feels that it Is justified In releasing this report at this time without the benefit

of the results of these studies because of the considerable amount of.data secured in the •

shorter studies, the urgent need for guidance In this field and the complete unanimity of

feeling among the committee members on the points covered. The committee does feel

that these studies should be completed and the results reported at the time of their

complerion.

18

CLASSIFICATION OF MEDIANS

Traversable Median - is one which consists of paint

stripes, buttons, an area of pavement of contrasting color or texture or a combination

of any of these. Its purpose should be obvious to the driver but it does not present a

physical barrier to traffic movements.

Deterring Median - is one which may incorporate any of the

features of a Traversable Median plus a minor physical barrier such as a rolled asphalt

curb, bars or corrugations, or ci mountable curb.

Barrier Median -is one which traffic will not cross intentionally.

It may be a barrier curb, a guard rail or some type of wall.

This report is the result of a considerable amount of

work by the committee and by the various agencies

assisting the committee. It is not possible to present

all of the information collected but it was felt that

the following examples serve to illustrate the find­

ings and are representative of the material assem-

bled.

19

Example 1 ... .. This example is a comparison of traffic operations on facilities with different

median designs. Figure 11 illustrates a section of roadway designed with a narrow (4 foot)

median and Figure 12 shows a similar section which utilizes a wide median with turning

lanes. The average volume on each of these facilities is approximately 18,000 vehicles

per day. The accident collision diagrams shown on these examples illustrate how the

median can be expected to affect the safety of a facility. The example shown in Figure 11

has considerably more accidents than the one shown in Figure 12.

20

ffi NOTE

3 PROVIDING

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COLLISION DIAGRAM OF ACCIDENTS

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TYPICAL EXAMPLE OF

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MEDIAN WITH TURNING LANE

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STUDY NO.4

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Example 2 ..... This example is similar to Example 1 with the exception that the average volumes

on the facilities are in the range of 21,000 to 27,000 vehicles per day. Figure 13 shows a

narrow median and Figure 14 indicates a wide median. A comparison of the accident

collision diagrams on these examples shows far fewer accidents where an adequate median

is provided.

22

GEOMETRIC LAYOUT AND

ROADSIDE DEVELOPMENT

TYPICAL MEDIAN LAYOUT

AND CROSS SECTION

COLLISION DIAGRAM OF ACCIDENTS

GEOMETRIC LAYOUT AND

ROADSIDE DEVELOPMENT

TYPICAL MEDIAN LAYOUT

AND CROSS SECTION

COLLISION DIAGRAM OF ACCIDENTS

TYPICAL EXAMPLE OF

NARROW MEDIAN

FIGURE 13

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WIDE MEDIAN WITH TURNING LANE

FIGURE 14 23

Example 3 ..... This example is similar to Example 1 with the exception that the volume on the

facilities is in the range of 33,000 to 37,000 vehicles per day. Figure 15 shows a narrow

median and Figure 16 shows a wide median. These examples show many more accidents

where a narrow four foot median is provided as compared with a wide median with left

turn lanes.

24

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Example 4 ..... This example iltustrates typical traffic operation on facilities which have similar

design but carry different volumes of traffic. A majority of the studies indicated that very

little operational difficulties were encountered when the volume was below 9,000 vehicles.

However, when daily traffic volumes exceeded this amount, serious accident and opera­

t lonal problems became obvious. Figure 18 illustrates operation below 9,000 vehicles per

day and Figure 17 illustrates operation with volumes over 9,000 vehicles per day.

26

COLLISION DIAGRAM OF ACCIDENTS

GEOMETRIC LAYOUT AND

ROADSIDE DEVELOPMENT

TYPICAL MEDIAN LAYOUT

AND CROSS SECTION

COLLISION DIAGRAM OF ACCIDENTS

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TYPICAL EXAMPLE OF

NARROW MEDIAN

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r <( a:: ~ I.J..I w

I o~c 3 I< :;! 2 w "I D " g , ~" ~ ~"

I rs~~<(g ~~i r ~ ~ ~ §~ §~ ~ ~

_J -i-------r 90' R.aw.

t= 68' BACK TO 8A 'I( OF VRB

64'-8" ASPHALT PAVEMENT

I t 230'

11-100' I

~: II' w. 6'-4" 12' 6' •• ]., "II' 12' 12' 4' 12'

I I I ~~LIGHTING ~TANDARD I I I CONC MEOIAN ~ T

I EACH END OF CONC MEDIAN~ .,. I PAINTED YELLOW t BEADED

_jJ ......___ 85%-40M.PH.

IHLdbJI ~~ - I

II IJ=- 11 ~· -~ n1 ~ - "

85%-38M.P.H.~

TYPICAL EXAMPLE OF

NARROW MEDIAN

FIGURE 18 27

STUDY NO. ll

Example 5 ..... This example illustrates typical operation on facilities which have no median or

traversable median designs. Figure 19 shows a typical no median study and Figure 20

shows a typical traversable median.

28

GEOMETRIC LAYOUT AND

RCADSIDE DEVELOPMENT

TYPICAL CROSS SECTION

GEOMETRIC LAYOUT AND

RCADSIDE DEVELOPMENT

RO.W.

10'

-B5%-36MRH

85%-36 M.P.H.-------..

120'

56' CROWN

44' ROBO. WOT.

12'

TYPICAL EXAMPLE OF

NO MEDIAN ARTERIAL

FIG.URE 19

,-----

= ~

10'

R.QW

STUDY NO. ZO

-------1 \____

--1 ~I

TYPICAL MEDIAN LAYOUT

AND CROSS SECTION

ROW

13'

120'

58' ROBO WDT

II' l if I // 1

14'

ROW I \..__ PAINTFO MEDIAN

~~ I~ ~L COLLISION DIAGRAM ~ ~ .-==:~========'--'===========~~~ '";;~~===:::{ OF ACCIDENTS ~ 9 71?. -"

~ 711 85%-36 MPH- 1/b-TYPICAL EXAMPLE

OF NARROW TRAVERSABLE MEDIAN

FIGURE 20 29

STUDY NO. 27

References A Policy on Geometric.Design of Rural Highways; Washington, D. C. ;American Associa­

tion of State Highway Officials; 1954.

A Policy on Arterial Highways in Urban Areas; Washington, D. C.; American Association

of State Highway Officials; 1957.

Traffic Engineering Handbook; New Haven, Connecticut; Institute of Traffic Engineers;

1950.

30