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服务水平

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标准编号: 服务水平
所属分类: 其他国外标准与工程资料
文件语言: 英语
文件格式: PDF
文件页数: 6 页
文件大小: 21.85 KB

· 更新：2026-10-30

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服务水平PDF 第 1 页 · 原页码 1

Figure 2-4. Minimum Turning Path for Intercity Bus (BUS-12 [BUS-40]) Design Vehicle

Max. steering angle is 41.9°

CTR = Centerline turning radius at front axle

服务水平PDF 第 2 页 · 原页码 2

Exhibit 2-32. Guidelines for Selection of Design Levels of Service
Functional class	Appropriate level of service for specified combinations of area and terrain type
Functional class	Rural level	Rural rolling	Rural mountainous	Urban and suburban
Freeway	B	B	C	C
Arterial	B	B	C	C
Collector	C	C	D	D
Local	D	D	D	D

Design Service Flow Rates

The traffic flow rates that can be served at each level of service are termed “service flow rates.” Once a particular level of service has been identified as applicable for design, the corresponding service flow rate logically becomes the design service flow rate, implying that if the traffic flow rate using the facility exceeds that value, operating conditions will fall below the level of service for which the facility was designed.

Once a level of service has been selected, it is desirable that all elements of the roadway are designed consistent to this level. This consistency of design service flow rate results in near-constant freedom of traffic movement and operating speed, and flow interruptions due to bottlenecks can be avoided.

The HCM supplies the analytical base for design calculations and decisions, but the designer should use his or her judgment to select the appropriate level of service. Exhibit 2-32 provides guidance that may be used by designers in selecting an appropriate level of service. For certain recreational routes or for environmental or land use planning reasons, the designer may possibly select a design service flow rate less than the anticipated demand.

Whether designing an intersection, interchange, arterial, or freeway, the selection of the desired level of service should be carefully weighed because the traffic operational adequacy of the roadway is dependent on this choice.

Weaving Sections

Weaving sections occur where one-way traffic streams cross by merging and diverging maneuvers. The principal types of weaving sections are illustrated in Exhibit 2-33. Weaving sections are designed, checked, and adjusted so that the level of service is consistent with the remaining highway. The design level of service of a weaving section is dependent on its length, number of lanes, acceptable degree of congestion, and relative volumes of individual movements. Large-volume weaving movements usually result in considerable friction and reduction in speed of all traffic. Further, there is a definite limit to the amount of traffic that can be handled on a given weaving section without undue congestion. This limiting volume is a function of the

服务水平PDF 第 3 页 · 原页码 3

Page	Existing Text	Corrected Text
3-88	Figure 3-18 should be updated.	Please substitute page 3-88 with the attached page that includes the revised figure.
3-92	The second sentence of the final paragraph on page 3-92 begins "The differences in track widths of the SU, WB-12, WB-19, WB-20, WB-20D, WB-30T, and WB-33D [SU, WB-40, WB-62, WB-67, WB-67D, WB-100T, and WB-109D] design trucks are substantial for the sharp curves associated with . . ."	Please change this sentence to read "The differences in track widths of the SU-9, SU-12, WB-12, WB-19, WB-20, WB-20D, WB-28D, WB-30T, and WB-33D [SU-30, SU-40, WB-40, WB-62, WB-67, WB-67D, WB-92D, WB-100T, and WB-109D] design trucks are substantial for the sharp curves associated with . . ."
3-94	The first note under Table 3-26b references the metric WB-19 design vehicle.	Please change this reference to the U.S. Customary design vehicle WB-62.
3-96	In the Radius of Curve column, the 2nd row value is listed as 25000.	Please change "25000" to "2500."
3-99	The final sentence in the section about Case II begins "Case I widths for these longer vehicles, including the WB-19, WB-20, WB-30T, and WB-33D [WB-62, WB-65, WB-100T, and WB-109D] design vehicles, may . . ."	Please change this sentence to read "Case I widths for these longer vehicles, including the WB-19, WB-20, WB-20D, WB-28D, WB-30T, and WB-33D [WB-62, WB-67, WB-67D, WB-92D, WB-100T, and WB-109D] design vehicles, may . . ."
3 103	Bottom section of Table 3 29	For clarification, add a row below "Application of Modification for Edge Conditions" with the headings "Case I, Case II, and Case III" in columns 2, 3, and 4, respectively; repeat in columns 6, 7, and 8 respectively.
3 114	The final paragraph on page 3 114 reads "The effect of rate and length of grade on the speed of a typical heavy truck is shown in Figures 3 24 and 3 25. From Figure 3 24 it can be determined how far a truck, starting its climb from any speed up to approximately 120 km/h [70 mph], travels up various grades or combinations of grades before a certain or uniform speed is reached. For instance, with an entering speed of approximately 110 km/h [70 mph], the truck travels about 950 m [2,700 ft] up a 6 percent grade before its speed is reduced to 60 km/h [35 mph]. If the entering speed is 60 km/h [35 mph], the speed at the end of a 300 m [1,000 ft] climb is about	Please change this paragraph to read "The effect of rate and length of grade on the speed of a typical heavy truck is shown in Figures 3-24 and 3-25. From Figure 3 24 it can be determined how far a truck, starting its climb from any speed up to approximately 110 km/h [70 mph], travels up various grades or combinations of grades before a certain or uniform speed is reached. For instance, with an entering speed of approximately 110 km/h [70 mph], the truck travels about 750 m [2,700 ft] up a 6 percent grade before its speed is reduced to 60 km/h [35 mph]. If the

服务水平PDF 第 4 页 · 原页码 4

GDHS-6-E1—November 2013*

Page	Existing Text	Corrected Text
	43 km/h [26 mph]. This is determined by starting on the curve for a 6 percent grade corresponding to 60 km/h [35 mph] for which the distance is 750 m ~~[2,500 ft]~~, and proceeding along it to the point where the distance is 300 m ~~[1,000 ft]~~ more, or 1050 m ~~[3,500 ft]~~, for which the speed is about 43 km/h [26 mph]. Figure 3-24 shows the performance on grade for a truck that approaches the grade at or below crawl speed. The truck is able to accelerate to a speed of 40 km/h [25 mph] or more only on grades of less than 3.5 percent. These data serve as a valuable guide for design in appraising the effect of trucks on traffic operation for a given set of profile conditions."	entering speed is 60 km/h [35 mph], the speed at the end of a 300-m ~~[1,000-ft]~~ climb is about 43 km/h [26 mph]. This is determined by starting on the curve for a 6 percent grade corresponding to 60 km/h [35 mph] for which the distance is 750 m ~~[2,700 ft]~~, and proceeding along it to the point where the distance is 300 m ~~[1,000 ft]~~ more, or 1050 m ~~[3,700 ft]~~, for which the speed is about 43 km/h [26 mph]. Figure 3-25 shows the performance on grade for a truck that approaches the grade at or below crawl speed. The truck is able to accelerate to a speed of 40 km/h [25 mph] or more only on grades of less than 5.5 percent. These data serve as a valuable guide for design in appraising the effect of trucks on traffic operation for a given set of profile conditions."
3-147	Equation 3-39 is shown as L = V² / [254(R ± G)] for the Metric units and as L = V² / [30(R ± G)] for the U.S. Customary units.	Please change Equation 3-39 to read L = V² / [254(R ± G)] for the Metric units and L = V² / [30(R ± G)] for the U.S. Customary units.
Chapter 4
4-2	Figure 4-1 incorrectly labels the traveled way and the roadway.	Please substitute page 4-2 with the attached page that includes the revised figure.
Chapter 5
6-13	Under Sight Distance, the final subsection of Section 6.3.1, the final sentence references Tables 6-2 and 6-4.	Please change this cross reference to Tables 6-3 and 6-4.
Chapter 9
9-12	The design speeds shown in U.S. Customary units in Figure 9-18 are incorrect.	Please substitute page 9-12 with the attached page that includes the revised figure.

服务水平PDF 第 5 页 · 原页码 5

GDHS-6-E1—November 2013*

Page	Existing Text	Corrected Text
9-45	In the 7^th row of Table 9-9 under U.S. Customary units, the Design Speed is listed as 4.	Please change this Design Speed to 45.
9-74	The dimensions for Diagram B in Figure 9-28 (Metric) are incorrect.	Please substitute page 9-74 with the attached page that includes the revised figure.
9-75	The dimensions for Diagram B in Figure 9-28 (U.S. Customary) are incorrect.	Please substitute page 9-75 with the attached page that includes the revised figure.
Chapter 10
10-78	In Figure 10-53, Part D2 incorrectly cross references Figure 10-69.	Please change the cross reference to "For Deceleration Length See Table 10-5."
10-93	Item 1 under Superelevation and cross slope refers to Figures 3-21 through 3-25.	The correct cross reference should be "Tables 3-8 through 3-12."
10-93	Item 3 refers to Figures 3-29 and 3-30.	Please change these cross references to Tables 3-15 and 3-16, respectively.
10-108	Note 2 in Figure 10-69 states, "Point A controls speed on the ramp. L_s should not start back on the curvature of the ramp unless the radius equals 300 m [100 ft] or more."	Please change "100 ft" to "1,000 ft."