Table of Contents

Mitigation Strategies for Design Exceptions – July 2007 (ARCHIVED)

Table of Contents

List of Figures

List of Tables

Introduction to Mitigation Strategies for Design Exceptions

Acronyms and Abbreviations

Chapter 1 - Design Exceptions

Design Exceptions

What is a Design Exception?

Why are Design Exceptions Needed?

Where are Design Exceptions Required?

Sources of Highway Geometric Design Criteria

The 13 Controlling Criteria

Types of Construction

Nominal and Substantive Safety

Substantive Safety

Comparing Nominal and Substantive Safety

Resources to Support Substantive Safety Analysis and Decision Making

Chapter 2 - The Design Exception Process

The Design Exception Process

1. Determine the Costs and Impacts of Meeting Design Criteria

2. Develop and Evaluate Multiple Alternatives

3. Evaluate Risk

4. Evaluate Mitigation Measures

5. Document, Review, and Approve

6. Monitor and Evaluate In-Service Performance

Summary

Chapter 3 - The 13 Controlling Criteria

The 13 Controlling Criteria

Traffic Operational and Safety Effects

Design Speed

Lane Width

Shoulder Width

Bridge Width

Horizontal Alignment

Superelevation

Vertical Alignment

Grade

Stopping Sight Distance

Cross Slope

Vertical Clearance

Lateral Offset to Obstruction

Structural Capacity

Chapter 4 - Mitigation Strategies

Mitigation Strategies

1. Design Speed

2. Lane Width and 3. Shoulder Width

4. Bridge Width

5. Horizontal Alignment and 6. Superelevation

7. Vertical Alignment

8. Grade

9. Stopping Sight Distance

10. Cross Slope

11. Vertical Clearance

12. Lateral Offset to Obstruction

13. Structural Capacity

Chapter 5 - Case Study 1 - Interstate 235 Reconstruction

Project Location

Project Description and Context

The Design Exception

Mitigation Measures

Discussion

Acknowledgements

Chapter 6 - Case Study 2 - Tensleep-Buffalo Highway - US16

Project Location

Project Description and Context

Site Constraints

The Design Exceptions

Mitigation Measures

Discussion

Acknowledgements

Chapter 7 - Case Study 3 - State Route 99 Reconstruction

Project Location

Project Description and Context

Improvements to SR 99

The Design Variance

Monitoring and Mitigation

Low-Profile Barrier

Discussion

Acknowledgements

References

Chapter 8 - Case Study 4 - State Route 110 - The Arroyo Seco Parkway

Project Location

Project Description and Context

Site Constraints

The Design Exceptions

Mitigation Measures

Discussion

Acknowledgements

Bibliography

Bibliography