Design			Search FHWA:
		FHWA > Infrastructure > Program Administration > Green Book

THE 2001 GREEN BOOK

Previous | Slides 9-24 | Next

---

Chapter 2
Design Controls and Criteria

Design Vehicles
Older Drivers
Design Speed Definition
Highway Capacity
Access Control and Access Management
The Pedestrian
Safety

---

Design Vehicles

Four classes of design vehicles:

• Passenger cars, include:
  • Cars, SUV's, Minivans, Vans, Pick-up trucks
• Buses (Separate category)
• Trucks
• Recreation vehicles

---

Design Vehicle

• Consider bicycles in selecting design vehicle when appropriate
• Added - Considerations in selecting design vehicle provided

---

Buses Added

Added:

• Two school bus configurations
• Intercity bus
• City transit bus

---

Trucks Turning templates revised Autoturn Centerline turning radius added Revised symbols Typical dimensions Turning characteristics defined Truck tractors added

---

Older Drivers

" . . . should be aware of the capabilities and needs of older road users and consider appropriate measures to aid their performance."

Expanded observations

Expanded countermeasures which may help alleviate potential problems

Older Driver Highway Design Handbook

---

Speed

• Definitions revised
• Running speed discussion condensed
  • two figures deleted
• Exhibit - corresponding design speeds in both systems of measurement

---

Operating Speed

OLD: highest overall speed at which a driver can travel on a given highway under favorable weather conditions and under prevailing traffic conditions without at any time exceeding the safe speed as determined by the design speed on a section - by - section basis

NEW: the speed at which drivers are observed operating their vehicles during free - flow conditions

---

Design Speed

OLD: maximum safe speed that can be maintained over a specific section of highway when conditions are so favorable that the design features of the highway govern.

NEW: a selected speed used to determine the various geometric design features of the roadway.

---

Speed

• Definitions revised
• Running speed discussion condensed
  • two figures deleted
• Exhibit 2 - 29 - corresponding design speeds in both systems of measurement

---

Speed

• Establishes:

  • Low - speed design: 70 km/h [45 mph] or less

  • High - speed design: 80 km/h [50 mph] or more

---

Traffic Flow Relationships

• Updated - consistent with 2000 HCM

• Exhibit 2 - 30 - Generalized speed - volume - density curve replaces two figures

---

Highway Capacity

Updated based on HCM 2000 Rewritten to eliminate duplication of material Exhibit 2 - 31 Generalized definitions of Level of Service replaces Level of Service Characteristics Refers user to HCM for details

---

Access Control
Access Management

• Rewritten and expanded to incorporate material from NCHRP 420
• Includes discussions on:
  • Basic principles
  • Classifications
  • Methods
  • Benefits
• 3 Exhibits on crash rates added

---

The Pedestrian

• Sidewalk - part of any street improvement
• Physical characteristics section replaced with Characteristics of Persons with Disabilities
  • Mobility, Visual, and Developmental
  • Added 600 mm [2 ft] detectable warning strips at bottom of sidewalk ramps
• Listed 7 measures to reduce pedestrian - vehicle conflicts
• Eliminates HCM duplication
• Level of service generalized

---

Safety

• Deleted tables and figure with accident data
• Emphasizes access control in reducing crashes
• Include adequate shoulders in narrow medians for:
  • Emergency stops
  • Use of emergency vehicles
• Added to list of factors to be considered in rural intersection design:
  • Crossroad sight distance
  • Type of highway

---

Previous | Slides 9-24 | Next