Chapter 4: Basic Design Criteria

4.1 Overview

Designs for highway and bridge projects are based on established design controls and criteria for the various elements of the project such as width of roadway, side slopes, horizontal and vertical alignment, drainage considerations and intersecting roads. This chapter provides descriptions of the traffic characteristics to be considered in selection of design controls and criteria for motorized transportation users.
This chapter discusses the basic design criteria that is applicable to all 4R projects and includes the following sections and subsections:
4.1 Overview
4.2 Speed
  • 4.2.1 Operating Speed;
  • 4.2.2 Running Speed;
  • 4.2.3 Design Speed;
  • 4.2.4 Target Speed; and
  • 4.2.5 Posted Speed.
4.3 Traffic Characteristics
  • 4.3.1 Traffic Volume;
  • 4.3.2 Design Vehicles;
  • 4.3.3 Control Vehicles; and
  • 4.3.4 Highway Capacity.
4.4 Access Management
4.5 Safety
4.6 Terrain
  • 4.6.1 Level Terrain;
  • 4.6.2 Rolling Terrain; and
  • 4.6.3 Mountainous Terrain.
4.7 Horizontal Alignment
  • 4.7.1 General Considerations;
  • 4.7.2 Curve Radius;
  • 4.7.3 Superelevation Rate;
  • 4.7.4 Superelevation Rates on Low-Speed Rural Town, Suburban, Urban and Urban Core Facilities;
  • 4.7.5 Superelevation Rate on Rural and High-Speed Suburban, Urban, and Urban Core Facilities; • 4.7.6 Superelevation Transition Length;
  • 4.7.7 Superelevation Transition Placement;
  • 4.7.8 Superelevation Transition Type; and
  • 4.7.9 Sight Distance on Horizontal Curves.
4.8 Vertical Alignment
  • 4.8.1 Grades;
  • 4.8.2 Vertical Curves;
  • 4.8.3 Grade Change without Vertical Curves;
  • 4.8.4 Vertical Alignment at Railroad Crossings;
  • 4.8.5 Vertical Alignment at Intersections; and
  • 4.8.6 Vertical Clearance.
4.9 Combination of Horizontal and Vertical Alignment
4.10 Cross Sectional Elements
  • 4.10.1 Through Travel Lanes;
  • 4.10.2 Speed Change Lanes;
  • 4.10.3 Shoulders;
  • 4.10.4 Pavement Cross Slope;
  • 4.10.5 Pavement Taper Lengths;
  • 4.10.6 Rumble Strips;
  • 4.10.7 Clear Zone;
  • 4.10.8 Lateral Offset;
  • 4.10.9 Border and Outer Separation;
  • 4.10.10 Right of Way Width;
  • 4.10.11 Roadside Design;
  • 4.10.12 Curbs and Curb/Gutter;
  • 4.10.13 Side Slopes;
  • 4.10.14 Safety Edge;
  • 4.10.15 Medians;
  • 4.10.16 Parking;
  • 4.10.17 Retaining Structures; and
  • 4.10.18 Utilities and Easements.
4.11 Sight Distance
  • 4.11.1 Stopping Sight Distance;
  • 4.11.2 Decision Sight Distance;
  • 4.11.3 Passing Sight Distance;
  • 4.11.4 Intersection Sight Distance; and
  • 4.11.5 Sight Distance at Under-Crossings.
4.12 Drainage Facilities
  • 4.12.1 Design Treatment of Cross Drainage Culvert Ends;
  • 4.12.2 Small Culverts;
  • 4.12.3 Intermediate Culverts;
  • 4.12.4 Large Culverts;
  • 4.12.5 Bridge Class Drainage Culverts;
  • 4.12.6 Parallel Drainage Culverts; and
  • 4.12.7 Side Ditches.
4.13 Environment
4.14 Human Factors
  • 4.14.1 Older Drivers & Pedestrians
4.15 Roadway Intersecting Department Projects