Grade Separated Structures

by June 12, 2020 · HIGHWAY

Grade Separated Structures

The type and location of various grade-separated structures (VUP, LVUP, PUP/ CUP, VOP) shall be as specified in Schedule ‘B’ of the Concession Agreement. In case the lateral/vertical clearance and the total length of viaduct required to be provided is different from the minimum specified in this Section, the same shall also be specified in Schedule ‘B’.

Grade Separated Structures

  1. The structures through which the traffic flows at different levels are called grade-separated structures.
  2. A grade-separated structure which is provided for the crossing of vehicles under the Project Highway is called as Vehicular Underpass (VUP)
  3. A grade-separated structure that is provided for the crossing of vehicles over the Project Highway is called Vehicular Overpass (VOP).
  4. A structure provided below the Project Highway to cross the pedestrians is called Pedestrian Underpass (PUP).
  5. A structure provided below the Project Highway to cross the catties is called Cattle Underpass (CUP).
  6. A pedestrian/cattle underpass through which light vehicles of height up to 3m can also pass is called Light Vehicular Underpass (LVUP)
  7. The flyover is synonymous with VUPA/OP.
  8. A structure provided above the Project Highway to cross pedestrians is called Foot Overbridge.
  9. A structure provided over the railway lines to carry the Project Highway is called Road Over Bridge (ROB).
  10. A structure provided below the railway lines to carry the Project Highway is called Road Under Bridge (RUB).
  11. A Trumpet interchange is a grade separator structure provided at major T-junction facilitating the uninterrupted flow of traffic for in each direction.
  12. A Cloverleaf is a grade separator structure provided at a major crossroad junction facilitating the uninterrupted flow of traffic in each direction.
Grade Separated Structures

Vehicular Underpass/Overpass (VUPA/OP)

The vehicular under/overpass structures shall be provided at the intersection of the Project Highway with all the National Highways and State Highways. Such under/overpasses shall also be provided across other categories of roads as per site requirements for the crossing of traffic. The structure may be either an underpass or an overpass depending upon the nature of the terrain, vertical profile of road and availability of adequate right of way, etc.

The decision, whether the crossroad or the Project Highway will be carried at the existing level, will be taken at the time of preparing the feasibility report and would be based on considerations of drainage, land acquisition, provision of ramps for the grade-separated facility, the height of embankment and project economy, etc.

Light Vehicle Underpass (LVUP)

The location of LVUP shall be specified in Schedule ‘B’.

Cattle/Pedestrian Underpass (CUP/PUP) and Foot over bridge

These shall be provided as specified in Schedule ‘B’ of the Concession Agreement

  1. A PUP/CUP/foot over bridge may not be necessary within a distance of 2 km from Vehicular underpasses/overpass and Light Vehicle Underpasses.
  2. The pedestrian crossings shall have provision for movement of physically challenged persons.
  3. Underpasses shall be preferred to foot overbridges.
  4. Pedestrian underpass/foot over bridge shall also be provided within a distance of 200 m from a school or hospital or factory/industrial area.
  5. The bus bays along with the bus shelters shall be provided at the pedestrian underpass/foot overbridge locations as specified in para 12.5 of this Manual.

The central portion open to sky position shall be so covered as to allow air and light, but not rain water.

Median Openings

Median openings of not less than 20 m shall be provided for emergency and for repair/ maintenance works with detachable guard barrier at a spacing of 5 km.

A separator between main carriageway and service road of the following type shall be provided to prevent the pedestrians, local vehicles and animals entering the highway.

Raised Footpath of minimum 1.5 m width with kerb on either side (200 mm above road surface), drain pipes across at minimum 10 m intervals and finished with CC paving blocks along with Metal Beam Barrier (Three Beam – one side) or pedestrian guard rail.

RCC/Cement Concrete lined drain-cum-footpath shall be provided at the edge of the service road (ROW side).

The raised footpath shall be depressed at suitable intervals to provide for convenient use of physically challenged persons.

Utility Corridor

A two-meter-wide strip of land at the extreme edge of ROW shall be kept for accommodating utilities, both over as well as underground. Provisions contained in IRC: 98 shall be followed to accommodate utility services in built-up areas of Project Highway. Utility ducts in the form of 600 mm diameter NP-4 Pipe across the Project Highway at a spacing of 1 km shall be provided for the crossing of underground utilities.

GEOMETRIC DESIGN AND GENERAL FEATURES

INTERSECTIONS AND GRADE SEPARATORS

Introduction

As mentioned in paras 1.13 and 2.12, there shall be no direct access to the main highway and all access shall be from service roads which shall be provided on both sides of the main highway and interconnected through underpasses, overpasses or grade separators. The existing direct access to the highway shall be closed and alternative access through service roads only shall be provided.

At-Grade Intersections

There shall be no at-grade intersection of any road with the main highway. But only with the service road. The intersection of the Project Highway with another National Highway (NH) or State Highway (SH) shall be grade separated. The existing direct intersections shall be closed and remodelled accordingly. The intersecting roads other than those mentioned above, shall be designed to facilitate all movements in following manner:

  1. Through underpass/overpass for crossing the Project Highway and then right turn through a ramp to merge with the Project Highway or service road if provided as per this Manual, or
  2. By merging with service road and crossing through the next available vehicular underpass.

There shall be interconnection between the service roads of both sides through underpasses which will facilitate cross movement of local traffic from one side to the other side and to facilitate change of direction of through traffic. Accordingly, the intersections on the service road including those at underpasses shall be designed for safe movements for all turnings.

Encompassing safety requirement and also to have better traffic control following layouts are suggested for at-grade intersections below structures on the project highway.

Grade Separated Intersections and Interchanges

An interchange is justified at locations where traffic on cross roads is moderate to heavy and for safe and efficient traffic flow, ramps are necessary for cross road traffic. The type and location of interchanges to be provided shall be specified in Schedule ‘B’.

Geometric standards for design

The geometric design standards for various elements of grade separators shall be as given in IRC:92. Gradient for approaches shall not be sleeper than 2.5 percent (1 in 40). ‘

Design of structures

Design of structures shall conform to Section 7 of this Manual. Minimum length of viaduct and RCC Retaining Wall/RE wall required to be provided shall be specified in Schedule ‘B’.

In case the length of Retaining/RE wall is not specified in the Schedule ‘B’, the same shall be deemed to be included in the scope of work and shall be provided as per site requirements.

Lighting

Lighting requirement shall be as per Section 12 of this Manual. The top and underside of the grade separated structures and interchange area at the ground level up to 50 m beyond the point from where flaring of the main carriageway takes place shall be provided with lighting.

The Concessionaire shall submit details of the ground surveys, traffic data, traffic forecast, traffic management and safety plan during construction, design, and drawings of the grade-separated intersections and interchanges showing all safety features to the Independent Engineer for review and comments.

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