Part 1: Table of Contents, Introduction and Background

Other parts of the report

Part 2: Noise Barrier Design Principles

Part 3: Design Prototypes

Part 4: Conclusions, References and Appencicies

Final Report, July, 1990
Prepared by Julie Farnham and Edward Beimborn
Center for Urban Transportation Studies
University of Wisconsin--Milwaukee
Milwaukee, Wisconsin 53201


The purpose of this report is to provide guidelines and suggestions for the improved design of freeway noise barriers in the Milwaukee region and elsewhere in the State of Wisconsin. The guidelines have been developed to encourage an attractive and efficient system of noise control and to achieve design continuity throughout the area. The report illustrates how inventories of the technical, cultural and natural landscape can be used in design. A variety of techniques of wall shape and texture and landscaping application are provided which can be adapted to specific environments. The desired approach views the wall and landscape as an integrated system that should be designed to reflect and enhance the surrounding community. Diversity in design of both the wall and landscaping should be sought and systems should be designed to reflect the historic/ethnic heritage of the neighborhoods. A broad range of options should be provided which can creatively enhance the environment that is seen as well as heard along freeways. The concepts developed in the study are illustrated through several prototype designs.

Sound good/look good.


Abstract i

Table of Contents ii

Acknowledgments iv

Introduction 1

Purpose 2

Report Organization 2

Goals and Objectives 3

Background 4

Noise Barriers Considerations 4

Criteria for Noise Barrier Installation 6

Design Guide 9

Basic Design Principles 10

Barrier Design 19

Landscape Plant Materials 30

Natural Landscaping 34

Uses of Landscaping for Aesthetics 36

Integration of Wall, Landform, and Plants 42

Lighting 50

Maintenance 52

Economic Considerations 54

Design Prototypes 55

Inventory and Analysis 56

Physical Patterns 56
Significant Views 58
Cultural Patterns 58
Land Use Patterns 60

Neighborhood Side of Barriers 64

Freeway Side of Barriers 70

Design Concept Alternatives 80

Site #1 -- Rural 82
Site #2 -- Suburban 86
Site #3 -- Urban Focal Point 86
Site #4 -- Urban Neighborhood 87
Site #5 -- Urban Gateway 94
Site #6 -- Historical Ghost 94

Conclusions 100

Bibliography 102

Appendices 105

Appendix A: Noise Barrier Material Costs 106
Appendix B: Plant Materials 108
Appendix C: Landscape Cost Comparison 119
Appendix D: Ethnic Neighborhood Descriptions 121
Appendix E: Site Analysis Checklist 124


This report was prepared in response to a legislative request included in the 1989-90 state budget to look at ways to improve aesthetic characteristics of freeway noise barriers. We would like to thank Rep. Timothy Carpenter for his support in this the project and for the help provided through his office by Paula Doyle and Curt Finkelmeyer in arranging meetings. A task force was established to guide this project including: Michael Gonia of the Wisconsin Department of Transportation, Kenneth Yunker of the Southeastern Wisconsin Regional Planning Commission, and John Erickson as represented by Robert Buffone of the City of Milwaukee. This task force provided useful insight and input on the project and we thank them for their assistance. We would also like to thank Linda Rupp for her expert help in processing and setting up this report. The opinions expressed in this report are those of the authors and not necessarily those of state or local government, the legislature, or the members of the task force.

Introduction and Background


These guidelines are primarily intended to serve as a tool for designers of freeway noise barriers in the Milwaukee metropolitan area. The primary purpose of establishing guidelines is to encourage an attractive and efficient system of noise control and achieve design continuity throughout the metropolitan freeway system. A secondary purpose of this report is to provide an analysis of the existing freeway environment to determine its unique characteristics and aesthetic opportunities.

Report Organization

This report includes three major sections: An introduction and background, a guide to the general aesthetic design of barriers and landscaping systems, and an application of the design guide to prototypical situations and opportunities along the I-94 freeway corridor in the southern part of Milwaukee County. Appendices provide more technical "catalog" information on available barrier and landscape materials.

Goals and Objectives

The goal of this project was to develop a process for system-wide planning for implementation of noise barriers which enhance and improve the aesthetic quality of Milwaukee County's freeway environment. This goal has two primary objectives:

1) To analyze the "system-wide" area to identify prominent physical and cultural patterns describing and expressing the character of Milwaukee County. This objective is based on the fact that barrier locations are not always continuous, but must fit into a continuous freeway environment. It is intended that an analysis of the system-wide environment will serve as the basis for integrating barriers into the overall urban context. Expressing these larger urban patterns could enhance the overall freeway environment and experience.

2) To explore alternative design solutions for barriers in site specific contexts. Specifically, these designs should accomplish the following:

i. To design new barriers and landscape as an integrated unit

ii. To integrate new barriers and landscape with existing barriers and landscape

iii. To design new walls to be as attractive as possible to minimize the need to screen with landscaping

iv. To design barrier and landscape to reflect and enhance specific cultural and physical characteristics of neighborhoods

Background: Noise Barriers Considerations

Noise barriers are being used with more frequency to solve problems of noise pollution from freeways in urban areas. Concern for the negative impacts of noise on the environmental quality of adjacent properties prompted the creation of federal and state regulations which require the placement of noise control measures in urban areas for new projects. Acceptable noise levels are often exceeded in nearly all segments of urban freeway with normal levels of freeway traffic. Consequently, noise barriers could be warranted for large portions of the freeway network and there could be a need to build extensive systems of noise barriers over the next decade. As a result of these concerns many cities and states are in the process of retrofitting their urban freeways with noise barriers. These projects are often implemented piecemeal without a comprehensive approach to integrate noise barriers into the urban environment. As a result they often appear as strictly technical solutions to the problem with relatively little attention given to their aesthetic impact on the environment.

Noise barriers can have a substantial effect on the visual environment of a highway and its surrounding environment. They are long continuous structures, often more than fifteen feet high, made of various materials. They can significantly change the view from the road by blocking view of the roadside and creating a monolithic uniformity of walls instead of changing urban scenery. They also can change the view towards the road for the surrounding community. There can be an increased sense of the noise barrier as a community barrier which separates an area from other places. Nonetheless, noise barriers may be highly sought after by neighborhoods as a means to reduce freeway noise levels. What is needed is a way to provide the benefits of the sound reduction which at the same time creating a positive visual image for road users and the surrounding communities. This report will suggest ways in which this can be done. Issues that need to be addressed in noise barrier design include:

1) Aesthetics: How to provide an attractive noise barrier that is complementary to and enhances the surrounding community and provides an improved urban image?

2) Cost: How to provide a barrier/landscaping system that has a reasonable cost to build as well as to maintain?

3) Effectiveness: How effective is the noise barrier in reducing sound levels?

4) Maintenance: How to minimize maintenance cost of the barrier and plant materials, how to minimize graffiti and potential legal/liability problems?

5) Safety: How to provide for a safe roadway and neighborhood, to protect safety of personnel performing maintenance activities, to maintain emergency access?

6) Acceptability: How to create a barrier/landscape system that can gain the enthusiastic support of the surrounding community as well as various political decision making groups?

Criteria for Noise Barrier Installation

The decision to install a noise barrier is based on criteria developed by the Federal Highway Administration and the Wisconsin Department of Transportation. FHWA permits states to use federal funds to install barriers along existing roadways and along new projects. WDOT had an administrative rule, TRANS 405, which sets criteria for barriers. These are as follows:

1) Noise barriers shall be designed to provide protection only to the ground floor of abutting buildings and not other parts of the buildings.

2) For the department to consider a site for construction of a noise barrier, the site shall meet the following criteria:

(a) For retrofit projects, a receptor shall be exposed to existing noise levels which equal or exceed the levels in Table 1.

(b) For new highway projects, a receptor shall have predicted future noise levels which equal or exceed the levels of Table 1 or which exceed existing noise levels by 15 decibels or more.

(c) A noise barrier protecting a receptor shall reduce noise levels by a minimum of 8 decibels.

(d) The total cost of a noise barrier may not exceed $30,000 in 1988 dollars per abutting residence. The department may annually adjust this $30,000 maximum figure up or down based on changes in the construction price index after 1988. Other land use categories shall be analyzed on a site specific basis to determine cost effectiveness.

The department can determine areas which are eligible for the installation of noise barriers through noise analysis. This is done chiefly by computer forecasts of sound levels using the

Background: Software

STAMINA software. Those areas which exceed the noise criteria shown in Table 1 can be identified. Eligibility for a barrier does not necessarily mean that one will be installed, since other criteria and budget must be considered. Furthermore priorities need to be set among various locations where barriers could be placed. Some of the parameters that could be used to set priorities are:

1) Number of dwelling units affected

2) Cost

3) Age of dwelling units versus age of highway

4) Forecast noise levels

5) Average daily traffic and

6) Noise insertion loss

Other factors such as citizen requests, geographic factors and input from other government agencies may also be considered.

Land Use


Leq(h)1 (dBA)

Description of Land Use Category
A 57


Lands on which serenity and quiet are of extraordinary significance and serve an important public need and where the preservation of those qualities is essential if the area is to continue to serve its intended purpose.
B 67


Picnic areas, recreation areas, playgrounds, active sports areas, parks, residences, motels, hotels, schools, churches, libraries, and hospitals.
C 72


Developed lands, properties, or activities not includes in Categories A or B above.
D --- Undeveloped lands.
E2 52


Residences, motels, hotels, public meeting rooms, schools, churches, libraries, hospitals, and auditoriums.
1"Leq" means the equivalent steady-state sound level, which in a stated period of time contains the same acoustic energy as the time-varying sound level during the same period. For purposes of measuring or predicting noise levels, a receptor is assumed to be at ear height, located five feet above ground surface.

"Leq(h)" means the hourly value of Leq.

2"Use of interior noise levels shall be limited to situations where exterior noise levels are not applicable.

History: Cr. Register, August, 1989, No. 404, eff. 9-1-89.

Part 2: Noise Barrier Design Principles