ANNEX B
ASEAN HIGHWAY STANDARDS

Table I ASEAN Highway Standards

Note:

1. Abbreviation: L = Level Terrain M = Mountainous Terrain R = Rolling Terrain

2.( ) = Rural (( )) = Urban

3. [ ] = Desirable Values

4. The right of way width, lane width, shoulder width and max. superelevation rate in urban or metropolitan area can be varied if necessary to conform with the member countries design standards.

ASEAN HIGHWAY DESIGN CRITERIA

1) Classification

ASEAN Highways shall be classified as shown in table 2

Table 2
Classification
(Based on Asian Highway Standards by ESCAP 1995)

"Primary" class in the new classification is the access controlled motorway. Access controlled motorway shall be used exclusively by automobiles. Access to motorway shall be done at grade-separated interchanges only. Motorcycles, bicycles and pedestrians shall not be allowed to enter motorway in order to ensure traffic safety and the high running speed of automobiles except when domestic legislation and regulation allow. At-grade intersections shall not be designed on motorway, and carriageway shall be divided by median strip. This class was newly included in the classification in view of the recent development of motorways in the member countries.

Class III can be used only when the funding for the construction and/or land for road is limited. The type of pavement should be upgraded to asphalt concrete or cement concrete as soon as possible in the future. Since Class III is also regarded as the minimum desirable standard, upgrading of any road sections below Class III to comply with the Class III standard should be encouraged.

Future traffic volume projected for 20 years after completion of road construction/ improvement (called Projected daily traffic volume hereinafter) should be used to determine the class of road as described below.

It is recognized internationally that the presence of heavy vehicles and slow-moving vehicles greatly influence the design of a highway. Therefore, in this classification, it is proposed to use the approach of "Passenger Car Unit (pcu)" which is widely used for design purposes in Asian countries. The flow coefficients shown in table 3 are used to convert vehicles into "Passenger Car Unit":

Table 3
Flow coefficients

The traffic volume of light vehicles does not need to be taken into account if exclusive lanes for light vehicles are provided. Flow coefficients for heavy vehicles can be increased if the road is located in a mountainous area.

Class of road is-determined as follows using "pcu" as an index representing traffic volume:

1. Determine "PDT" or "projected daily traffic volume (pcu/day)" using projected traffic volume by vehicle type (vehicle/day) and flow coefficients.

2. Determine "K value" which is the ratio of the 30th highest hourly traffic volume over one year (pcu/hour) to annual average daily traffic (pcu/day). Traffic count data on a road section which has similar characteristics to planned road can be used. K value is usually around 0.10.

3. Determine "D value" which is the ratio of heavy directional- peak hour (30th highest) traffic volume (pcu/hour) to both directional peak hour (30th highest) traffic volume (pcu/hour). D value usually ranges from 0.55 to 0.60.

4. Calculate "PPHT" or "planning peak hour traffic volume (pcu/hour)" using a formula PPHT = PDT x K x D. PPHT represents projected heavy directional 30th highest hourly traffic volume (pcu/hour).

5. Divide PPHT (pcu/hour) by 1,800 (pcu/hour) which is widely recognized as standard capacity per one lane and round up the calculated value to determine number of lanes in one direction. Multiplying by 2 gives the required number of lanes (both directions).

6. Determine the class according to the required number of lanes determined in step v). "Primary" class can be used if the development of access controlled motorway is needed.

2) Terrain classification

Terrain classifications shown in table 4 shall be used.

Table 4
Terrain classification

3) Design speed

The relation between design speed, highway classification and terrain classification is shown in table I Design speed of 120 km/h shall be used only for Primary class (access controlled motorways) which have median strips and grade separated interchanges. Recommended design speed in urban shall be used :

Class Primary 80-100 k.p.h.
Class I       60-80 k.p.h.
Class II      50-60 k.p.h.
Class III     40-50 k.p.h.

4) Cross section

The dimension, such as right of way width, lane width, shoulder width, for each highway classification are shown in table 1.

It is highly recommended that pedestrians, bicycles and animal-drawn carts be separated from through traffic by provision, where practical, of frontage roads and/or sidewalks for the sections where smooth traffic is impeded by the existence of this local traffic.

5) Horizontal alignment

Horizontal alignment shall be consistent with the topography of the terrain and should provide forsafe and continuous operation at a uniform design speed. Horizontal alignmentmust afford at least the minimum stopping sight distance for this design speed.

In the design of highway curves it is necessary to establish the proper relation between design speed and curvature and also their joint relations with superelevation and side friction

Radius of curvature is calculated from

               v2
     R = -------------
          127.5 (e+f)

Where    v = Design speed ( Kph. )
         e = Rate of roadway superelevation m/m
         f = Side friction factor
         R = Radius of curve ( m. )

Table 5
Recommended side friction factor

The minimum curve radius is a limiting value of curvature for a given design speed and is determined from the formula above using the maximum superelevation rate suggested and the related side friction factor. Minimum curve radius shall be applied only when necessary and shall be used in conjunction with transition curve which is also recommended for longer curve, the values larger by so to 100 percent should be considered as the design normal curve radius.

The widening along the horizontal curves should be provided which is based on the design speed, the pavement width the radius of curve and the dimension of the standard truck.

Minimum horizontal curve radius in Urban recommended:

Class Primary   230 m.
Class I         120 m.
Class II         75 m.
Class III        50 m.

6) Vertical Alignment

The vertical alignment of any highway shall be as smooth as it is economically possible, that is, there shall be a balance of cutting and filling to eliminate the rolling nature of land. In the use of the maximum vertical gradient, it shall be kept clear in the mind of the designer that, once constructed to a given vertical grade, the highway cannot be upgraded to a lesser gradient without the loss of the entire initial investment. The maximum vertical grade shown in table I shall be used. The minimum vertical curve length shall be based on the algebraic difference in grades , the design speed and the minimum stopping sight distance.

The critical length of gradient section for the provision of a climbing lane is recommended to highway classifications Primary and Class 1, as shown in table 6

Table 6
Critical length of gradient section for the provision of a climbing lane

It is desirable to provide a climbing lane to the up-gradient highways with heavy truck traffic where the length of gradient exceeds the above values.

7) Pavement

Carriageways should be paved with cement or asphalt concrete. Only in cases where the anticipated traffic volume is quite low will bituminous treatment be adopted as surfacing. It is also recommended that the shoulders be paved with cement or asphalt concrete or be surfaced with bituminous materials.

However, as road pavement is designed taking into account i) maximum wheel load which should be based on the standard trucks ii) traffic volume iii) Design life iv)qualities of materials to be used.

8) Bridge

Bridges and culverts should be built as permanent structures. For minor bridge shorter than 50 meters , the full roadway width should be carried through including the width of shoulders. The minimum width between curbs for a major bridge longer than 50 meters should be one half meter greater than the width of the pavement approaching it. Walk way should be provided at one meter wide but for long spans can be limited to one side of the bridge only.

9) Structure loading

Increasing heavy traffic, particularly container traffic, requires properly designed load capacity (maximum axle load). In order to prevent serious damage to road structures, and also to reduce maintenance costs, the ASEAN and the Asian Highway network, as an international road network, should have high design load capacity.

The minimum design loading of HS20-44, which is the international standard corresponding to full-size trailer loading, shall therefore be used for design of structures.

10) Vertical clearance

Minimum vertical clearance shall be 4.5 in, which is the requirement for safe passage of standard ISO containers. However, in cases where sufficient clearance cannot be secured because of the high cost of rebuilding existing structures such as bridges, goose - neck trailers with low vehicle bed clearance could be used. Generally the desirable vertical clearance should be 5.00 in.