School of Civil Engineering孙仁娟

2013-02-26

URBAN ROAD DESIGN

Chapter 1- Introduction

The Foreword of the AASHTO 2004 “A Policy on Geometric Deign of Highways and Streets” states:

“As highway designers, highway engineers strive to provide for the needs of highway users while maintaining the integrity of the environment. Unique combinations of design requirements that are often conflicting results in unique solutions to the design problems…Sufficient flexibility is permitted to encourage independent designs tailored to particular situations.”

A Policy on Geometric Design of Rural Highways, 1954 and 1965 editions; A Policy on Arterial Highways in Urban Areas, 1957; A Policy on Design of Urban Highways and Arterial Streets, 1973; Geometric Design Standards for Highways Other Than Freeways, 1969; A Policy on Geometric Design of Highways and Streets, 1984, 1990, 1994, 2001, 2004, and 2011

Road Urban road Rural road Highway Collector Street Expressway Freeway

Components

Classifications and grades

Controls and criteria

Capacity and LOS

Construction boundary

Contents

Components

Motorway, non-motorway Sideway-pedestrian Green belt Drainage system-gutter, gutter inlet, drain well Traffic facilities-Traffic light, traffic sign, traffic island, traffic guardrail, traffic control system Traffic crossing, traffic intersection Parking lot, bus station Lighting facilities Underground pipelines: electric cables; gas pipe lines; communication wires; water supply and drainage systems; storm water sewer; Other: viaduct; pedestrian overpass; pedestrian underpass

Classifications and grades

Classification: Freeway, arterial road, minor arterial road, and branch road - Freeway: 在城市内修建的，中央分隔、全部控制出入、控制出入口间距及型式，具有单向双车道或以上的多车道，并设有配套的交通安全与管理设施的城市道路。 ( 《 城市快速路设计规程》 CJJ129-2009) - Arterial road: 连接城市各主要分区的干路，以交通功能为主 ( 《城市道路设计规范》 CJJ37-90) - Minor arterial road: 与主干路结合组成干路网，起集散交通的作用的道路，兼有服务功能。 ( 《城市道路设计规范》 CJJ37-90) - Branch road: 联系次干路或供区域内部使用的道路，解决局部地区交通，以服务功能为主。 ( 《城市道路设计规范》 CJJ37-90)

Grade : I 、 II 、 III

Controls and criteria

An initial step in the design process is defining the function that a facility is to serve.

The ability of the roadway to provide that function is related to the anticipated volume of traffic, the anticipated operating speed, and the geometric criteria present.

Controls and criteria

Design SpeedThe Design Speed is a selected speed used to determine the various geometric design.The Design Speed chosen for a road is a major factor in choosing superelevation rates  and radii of curves, sight distance, and the lengths of crest and sag vertical curves.

Controls and criteria

Design Vehicles Design Vehicles are selected motor vehicles with the weight, dimensions, and operating characteristics used to establish highway design controls for accommodating vehicles of designated classes. The design of the road is significantly affected by the type of Design Vehicles, including horizontal and vertical alignments, lane widths, turning radii, intersection sight distance.

Controls and criteria

Design Vehicles

Controls and criteria

Design Vehicles

Controls and criteria

Design Hour Traffic VolumeAverage daily traffic (ADT)Average daily traffic (ADT)Peak Hour Traffic Peak Hour Traffic Directional distributionDirectional distribution

kNN dah

Controls and criteria

Design period

Controls and criteria

Load standard

Cement concrete pavement & asphalt pavement: Single axle-dual wheel 100KN (BZZ100)

Bridge and tunnel

Controls and criteria

Anti-disaster standard

地震动峰值加速度 （ Seismic peak ground acceleration ）：

地震烈度： Ⅶ Ⅷ Ⅸ Ⅹ峰值加速度平均值： 0.125g 0.25g 0.5g 1.0g

道路工程设防地震动峰值加速度系数起点应为 0.20g,以下情况设防起点应为 0.1g ， 1 ）高填方路基边坡或深挖方路堑边坡，地震时可能产生大规模滑坡、塌方的重要路段。 2 ）重要附属构筑物如高挡土墙、高护坡、高护岸等。 3 ）软土层或可液化土层上的道路工程。地震动峰值加速度系数为 0.1g 以下可不设防。

Controls and criteria

Anti-disaster standard

Flood control and prevent waterlogging

Capacity and LOS

Capacity of a facility is the maximum hourly rate at which persons or vehicles reasonably can be expected to traverse a point or a uniform section of a lane or roadway during a given time period under prevailing roadway, traffic, and control. Vehicle capacity is the maximum number of vehicles that can pass a given point during a specified period under prevailing roadway, traffic, and control conditions.Person capacity is the maximum number of persons that can pass a given point during a specified period under prevailing roadway. Person capacity is commonly used to evaluate public transit services, high-occupancy vehicle lanes, and pedestrian facilities.

Capacity and LOS

Level of service (LOS) is a quality measure describing operational conditions within a traffic stream, generally in terms of such service measures as speed and travel time, freedom to maneuver, traffic interruptions, and comfort and convenience. Six LOS are defined for each type of facility that has analysis procedures available. Letters designate each level, from A to F, with LOS A representing the best operating conditions and LOS F the worst.Each LOS represents a range of operating conditions and driver’s perceptions of those conditions.

Capacity and LOS

Capacity and LOS

Urban Street Class Ⅰ Ⅱ Ⅲ Ⅳ

Range of free-flow

Speeds (FFS)

55 to 45 mi/h 45 to 35 mi/h 35 to 30 mi/h 35 to 25 mi/h

Typical FFS 50 mi/h 40 mi/h 35 mi/h 30mi/h

LOS Average Travel Speed (mi/h)

A

B

C

D

E

F

＞ 42

＞ 34-42

＞ 27-34

＞ 21-27

＞ 16-21

≤16

＞ 35

＞ 28-35

＞ 22-28

＞ 17-22

＞ 13-17

≤13

＞ 30

＞ 24-30

＞ 18-24

＞ 14-18

＞ 10-14

≤10

＞ 25

＞ 19-25

＞ 13-19

＞ 9-13

＞ 7-9

≤7

Capacity and LOS

Service volumeVolume: The number of persons or vehicles passing a point on a lane, roadway, or other traffic-way during some time interval. Often 1 hour, expressed in vehicles, bicycles, or persons per hour.Volume to capacity ratio: The rate of flow rate to capacity for a transportation facility.Service volume: The maximum hourly rate at which vehicles, bicycles, or persons reasonably can be expected to traverse a point or uniform segment of a roadway during an hour under specific assumed conditions while maintaining a designated level of service.

Capacity and LOS

Construction boundary

Questions?