Road design manual

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Approach

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To get to a design which is comprehensive and looks at all aspects of the road, we go about it in the following way.

First, we list all possible uses of a road. These include, but are not limited too vehicular (2,3 & 4 wheelers), bicyclists, pedestrians, bus-stops and other street furniture such as streetlights, electric lines, utility lines, drainage and sewerage, parking, hawkers etc. Make a comprehensive checklist to make sure all possible utilizations are included.

Next, for each of these uses, we list down all the requirements. To come up with these requirements, we need to place our selves in position of the user/utility provider and look at what would be required to meet the above mentioned objective. In addition, one needs to look at  specifications and guidelines of the IRC (Indian Road congress) and equivalent international standards. These will then be collated and organized in a systematic manner.

Once the requirements of each of the use cases has been obtained a detailed checklist needs to be formed, which would incorporate all the requirements for all the uses. As one goes through the process of road design, one should ensure at the end of it that the checklist is gone through and all have been met.

It would be cumbersome to do this process for each road that comes up. Not only this, if we come up with a different design each time, the lack of consistency will confuse road users and lead to further accidents. Hence, it is imperative that this be standardized to some extent. The way this can be done is to build a reference design. These essentially have the plan view and section view of a typical road section. For any new road, this should be adhered too.

Now obviously one reference design will not suffice for the variety of roads that are in use in a city. For example, a residential road will look quite different from an arterial road. Thus there is a need to make many such reference designs for a variety of roads. To do this, roads should be categorized depending on their primary use and width. A reference design should be then done for each of these road types. This becomes a template developed for these type of roads, and one would have a template for each road type.

Lastly, for this to have an impact city-wide, these templates should be mandatory part of the road specifications and tendering process. If the road developed is given to a private contractor, it should be ensured that the geometric design is specified and the given template is adhered too. Over time, this will ensure all roads have a basic uniformity, as well as are optimized to meet the local need and the broad objectives set out at the beginning of the document.

 

Classification of Roads

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As we explained in section 3, it is impractical to go through the design process for every road. In addition, it is desired that there is a basic degree of standardization across all the roads in a city. To this end, we need to build design templates which can be then used at the construction of any new road that is being built. Given the variety of roads, there is a need to classify them depending on use and widths.

The IRC2,7 classifies the roads as under:

1.      Expressway: Function of expressways is to cater for movement of heavy volumes of motor traffic at high speeds. They are generally signal free by providing with grade separation at intersections. Parking, loading and unloading of goods and pedestrian traffic are not permitted on these roads.

2.      Arterial: A general term denoting a street primarily for through traffic, usually on a continuous route

3.      Sub-arterial: A general term denoting a street primarily for through traffic usually on a continuous route but offering somewhat lower level of traffic mobility than the arterial

4.      Collector street: A street for collecting and distributing traffic from and to local streets and also for providing access to arterial streets

5.      Local street: A street primarily for access to residence, business or other abutting property.

 

The above is a good primary classification. In addition, the following should be used for further granularity

1.      Width: Since the design and traffic capacity of a road depends on the width, this should be a necessary parameter while classifying the road.

2.      Zone of use: That is, is this primarily in a residential, commercial or office area. Since usage patterns, parking, pedestrian requirements vary significantly between the above, this is also a necessary parameter while classifying a road

3.      Special uses: For example, is this road supposed to support BRTS. Or does this support a cycle track. Again, since for these types, the design template will need to be specially done, they need to be included in the classification.

 

So, as an example, one type of road based on this classification could be

Collector street, commercial, 24m width.

This needs to be worked out so that almost all (at least 90%) of the roads in the city can be covered in this classification

A similar approach and template designs are covered in IRC7. However, these reference designs are not comprehensive, and are primarily done only to give the desired width requirements.

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Design Example

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Here we run through a real life example of a stretch of a road. We will look at the current state of this stretch of road, go through its uses as listed in section 4, and see the requirements of each of its uses as mentioned in section 5. Based on this, we will list out possible designs and explain how it will improve the road with respect to the objectives enumerated in section 2.

 

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Design templates for each road type

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Based on the above classification, a number of road types were obtained in section 7. As mentioned in section 3, we are here proposing a reference design/ design template for each of the road type enumerated above.

 

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Introduction

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Streets are the very heart of urban living. They are the ones which provide mobility for men and material. They are also used for water, sewerage, telecom, electricity distribution alike. They also to a large extent determine the character of the city. Well designed and well maintained streets can make all the difference between the perception of a developed country and a developing one.

In this document, we deal with streets in the urban and semi-urban context. Streets and roads are used interchangeably to mean the same thing.  When building a road, there are different aspects which come into play. We can classify them as under

·        Geometric design

Relating to the road layout, i.e. the plan view and section view from an engineering drawing viewpoint. Thus, the width of pavement(vehicular portion), footpaths, intersection design, position of streetlights, trees & street furniture, height of kerb etc all come under this

·        Civil engineering

Relating to the actual materials, quality of construction. Implementation of a given geometric design would mostly fall in this classification.

·        Non engineering

These could be the actual tendering process, financials, systems for monitoring and maintenance etc.

Our focus is going to be the geometric design aspect. The geometric design of streets can make a huge difference how efficiently it carries out its functions, and its safety.

 

Objective

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The general expectations from a street are listed below. In other words, these are the principles/objectives on which street design should be based.

1. Safety

This is the primary concern. A road should be safe for all users, including and specially pedestrians, bicyclists, the elderly and the handicapped. In the absence of good designs and enforcement, might is right rules, traffic can be chaotic and unsafe.

2. Ease of navigation

We frequently have faced situations when a parked car is abutting a road, or pedestrians standing in the middle of the road causing the vehicle driver to swerve, or at U-turn with cars piled up obstructing the straight moving traffic. All this results in the driver always on the edge, and can never relax. This makes the whole driving experience a stressful one. Similar is the case with pedestrians. With no clear cut footpath or at intersections it can be a very stressful experience just crossing a road. This need not be the case.

Ease of navigation can always be achieved, as against speed of navigation. Speed depends on the road available and traffic. However, navigation, irrespective of traffic density, both of pedestrians or vehicles can be made easier and stress free by better designs of roads and intersections.

3.   Quick and smooth movement

Design should ensure quick and smooth movement of vehicles. This does not mean that vehicles should go with high speed, rather that they can maintain a decent average speed over their drive.

 

4. Aesthetics

Pretty, Neat, Clean and Green.

Should be beautiful and beautiful roads is what  makes the city look pretty.

Neat, with clearly marked lanes, straight footpath edges, no protrusions, are all required of the road.

Of course, cleanliness should be maintained.

Roads present a wonderful opportunity to add to the green cover of the city. Trees and other greenery along the roads can make it a very pleasant experience.

 

5. Optimal space utilization

To achieve all the above, we must keep in mind that space is at a premium in the urban cities. All the above must be achieved within the given or reasonable width of road. To do this one must design innovative and efficiently.

 

Thus the roads must be comprehensively designed to make efficient use of available space, taking into account all its uses. Examples of some functions are street furniture such as bus-stops, street lighting, utility lines such as electrical, water and drainage, cables etc.

 

What are the requirements/ specifications of each aspect of the road, so as to meet the above objectives ? How does one approach the design to meet the above ? This are some of the things this document is about and we will address theses in the coming sections

 

References

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1.      Guidelines on regulation and control of mixed traffic in urban areas. IRC:70-1977

2.      Geometric design standards for urban roads in plains. IRC:86-1983

[This document for cross-fall contradicts itself between section 6.2.5 (2.5% to 3%) and section 8.4 (3 to 4%). Ref 4 goes by max of 2.5% and we will go with the former guidance]

3.      Guidelines for pedestrian facilities IRC:103-1988

4.      Accessible bus-stop design guidance

Bus Priority technical team advice note BP1/06, January 2006

Transport of London

5.      Manual for streets

Department of transport

Thomas Telford publishing

6.      Accesscode: a Code of Practice on Access and Mobility

An advisory code reflecting current statutory requirement and best practice within the UK.

http://www.accesscode.info/

      7.  Space standards for roads in urban areas: IRC:69-1977

 

 

Requirements/Specification for each use

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Requirements of each use case will be listed comprehensively, taking inputs from multiple sources. Were possible, the requirement will be specified numerically. The first source for the requirements would be IRC documents. In case requisite IRC guidelines are unavailable or insufficient, other national standards(primarily UK) are used.

Envioremental functions

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5.1.1      Trees

5.1.2      Garbage bins

5.1.3      Rain water run off

 

People Movement

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5.1 

5.1.1      Thoroughfare for motorized vehicles

a)      2 wheelers

b)      3 & 4 wheelers, light commercial vehicles

c)      Greater than 4 wheelers, heavy commercial vehicles.

 

5.1.2      Thoroughfare for non-motorized vehicles

a)      Pedestrians

1.      Width of footpath [also called side-walk]

IRC guidelines1 stipulate that the minimum width of a footpath should not be less than 1.5m. Width should depend on pedestrian traffic, varying between 1.5m at a minimum to a maximum of 4.0m.

However, in addition to providing footpath for pedestrians, it is equally important to see that this complete width is always available throughout the road and is unobstructed. Frequently, we observe that if the footpath is not clear, either because of hawkers, parking, bus-stops etc. So part of providing a quality footpath is to provide different spatial arrangements for these.

Electric Box and tree obstruct the  footpath and make it unusable

Whenever there is a constriction in the footpath, the person in order to skip it will walk on the road. Then, even if a clear stretch of footpath is available, there is a tendency to continue walking on the road. Also, a pole in the middle will halve the space available for the wheelchair, and may make it unusable for the handicapped. Hence, the footpath should be unobstructed throughout. To enable this, street furniture such as electrical poles, lamp posts, trees etc should be placed one edge of the footpath and not arbitrarily somewhere on the footpath. Similarly pole transformers should be at such a height so as to not obstruct pedestrians.

Where absolutely unavoidable, in presence of localized obstructions, the unobstructed width of a footpath should not be less than 1m to allow a wheelchair(815mm) to pass comfortably. Overhangs if any should be at a height greater than 3m from the footpath level.

2.      Kerb Height

A high kerb forces the car park away

The footpath would usually be at a slightly elevated height referred to the paved road. This gives protection to the pedestrians, prevents vehicles from coming over to the footpath and helps better segregation. Kerbs may be provided at the road edge to increase this segregation. The IRC2  recommends kerb heights between 325mm to 200mm on the road side with the footpath elevation of 125mm with respect to the paved road.

However, we find that, this height is more than the clearance of vehicle doors (~250mm). So in the case of parallel parking, it becomes inconvenient to open the passenger side door of the car. This results in the vehicle being parked at a distance from the kerb, thus using valuable road space.

Hence, it is recommended that in case there is provision for parking adjacent to the footpath, the additional kerb barrier be done away with. That is, the footpath is maintained at an elevation of 125mm with respect to the paved road, and no additional kerb is placed.

3.      Access ramp or Dipped Kerbs

Footpaths need to be frequently broken for cross-roads, car parking ramps and other reasons.  Usually it is observed that in such a case, the footpath is stopped abruptly. This makes it inconvenient for pedestrians and becomes impossible for the wheelchair bound to get on to the footpath. Hence a gradual gradient must be given, which should not exceed 1:9.6 Care should be taken to make it non-slip.

4.   Identity maintained

Whenever the footpath is broken for certain distance, because of cross-roads, intersections, car parking ramps and others, the identity of the footpath should be maintained. This means, as far as the pedestrians are concerned, the footpath would continue in a similar form on the paved road. Thus, that part of the road is of the similar texture of the footpath. This would make it easier for pedestrians as they clearly know what area to walk on, and for the vehicle drivers would to be extra cautious as they drive on that area.

Figure on the left shows how the footpath gives up its identity for an off lane. On the right one can see how the identity of the footpath is maintained, infact enhanced even more.

5.   Crossfall

The IRC guideline2 here stipulates that the crossfall should be within the range of 2.5% to 3%. If it is too flat, it is difficult to drain, whereas if it is too steep, it would get dangerous to walk on.

 

6, Surface quality

They should have an even, firm, well-drained surface which is non-slip in both wet and dry weather. Joints should be closed and flush to prevent small wheels, walking sticks and canes from becoming trapped.

Covers and gratings in particular should be flush with the surface, nonslip, and have no openings greater than 13mm wide6. It is preferable to avoid the use of gratings or 'slot' type drainage within pedestrian areas and at pedestrian crossing points because they can trap small wheels and canes. However, if this is not possible, then gully covers and drainage slots should be positioned as far as possible from and at right angles to the main pedestrian flow lines.

The surface color should contrast with that of the surroundings, and especially that of the road used for vehicular traffic.

 

7.Longitudinal gradients

For pedestrians and especially for wheelchair bound, sudden or irregular gradient changes should be avoided, with gradients kept to 1:20 or less wherever possible.  Wherever this is not possible, a maximum gradient should never exceed 1:12.6

 

Optional

8. Markings to aid blind people

While this is highly desirable, good quality footpath which maintain 1 to 7 above should be first achieved. Then one needs to begin working on making these disabled friendly.

No IRC guidelines on this aspect are available. However, there are a number of other national standards5,6 which have detailed guidelines for these.

9. Verge and  barrier

Verges or nature strips, in addition to beautifying the road, are useful to accommodate electric poles, lighting columns. In addition, they ensure proper vehicle placement and development of full carriageway capacity (IRC2).  They also improve segregation between footpath and the paved road. Wherever space is available, verges with minimum of 1m width should be given.

Wherever appropriate, pedestrian guard-rails can be given (IRC1). One must be aware that it would not be beneficial to provide parallel parking where guard rails are present as one would need to park at a distance to be able to open the vehicle door. Hence, angular parking must be provided wherever parking is provided next to a guard rail.

Guard –rail helps the control and regulation of pedestrian traffic.  However, if quality footpaths are not provided, pedestrians are likely to use the paved road and will be further dissuaded from using the footpath even in quality streches.

Guard-rail designs are given in IRC3

 

 

b)      Bicyclists

                                                                                        

5.1.3      Street intersections, turns and  pedestrian crossings

a)      3 intersection streets

b)      4 intersection streets

c)      Multi intersection streets

d)      Roundabouts

e)      Single turns from and into the street

f)        U-turns

g)      Standalone pedestrian crossings

 

Static Uses

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5.1 

 

5.1.1      Parking

a)      2 wheeler parking

b)      4 wheeler private parking

c)      3 wheeler[rickshaw],Taxi and Para-transit parking

 

5.1.2      Hawkers

 

5.1.3      Bus-stops and transit facilities

1.      Location

·        Conveniently located for pedestrians

o       Unobstructed access to and from stop

o       Preferably close to pedestrian crossing

o       Should keep in mind that Q can build up beyond the stop itself and certain area should be kept free for passengers beyond the stop

·        Minimizes disturbance to regular flow of traffic.

o       Should not be so close to main junction so as to affect road safety or junction operation

o       Should not be at the entry/exit ramp of a flyover as that creates unnecessary pile up

·        Clear of parking and other street furniture

o       Dissuade other vehicles from parking near bus-stop area

o       Should not have street furniture which would obstruct buses or bus-passengers accessing the bus-stop

·        Visibility

o       Driver should get clear view of passenger

o       Passengers should get clear view of approaching bus and its number/destination

·        Access to other bus-stops

o       Should be situated to minimize walking distance between interchange stops

o       Tail to tail, on opposite sides of the road, preferably with a pedestrian crossing between them.

o       Distance between bus-stops. Depending on locality, the distance should not be excessive (> 2 km) as this would burden passengers. Similarly bus-stops should not be too close (< 0.5 km) as this would slow down the bus service.

 

2.      Information

·        Bus-numbers, bus-routes and bus timings

o       Critical, but not done. Bus-stops should clearly have the bus numbers that stop at their stop, their routes and destinations and timing information.

o       Name of bus-stop. Should be visible from the bus as well as from a distance for pedestrians

·        Maps

o       A city map which indicates all the bus routes and rational behind the bus numbering

·        Standardisation

o       Above should be standardized, so that each bus-stop looks and feels identical. This will help quickly finding the relevant information for passengers.

 

 

3.      Shelter design

·        Seating arrangement

o       Are there adequate seating/standing berths depending on loading at that stop

o       Is the seating arrangement easy to clean and maintain, given its heavy use

o       It should facilitate the Q system. If there are multiple buses accessing a stop, it should be possible for passengers to access it without disturbing the Q system

o       Incoming bus and number visible from where seated

o       Protection from the elements, ie sun and rain

·        Box design aspects

o       Should not obstruct pedestrian footpath

Design should be such or placed such that the footpath is not obstructed/reduced or minimally altered

o       Entry/Exit should be facilitated

Passengers entering the bus and those alighting from the bus should not conflict, with smooth movement of both

o       Prevent spillover to road

We observe that passengers tend to spill over to the road and wait on the road. This results in the bus stopping away from the stop, further inconveniencing passengers in the stop. In addition, this takes a higher portion of the road, also makes it unsafe for the passengers. Design should take this aspect into account, and see if a barrier for spilling over into the road can be incorporated.

o       Height of kerb

While getting into the bus, if the kerb is at a height, this will facilitate entry to the bus. Also it will give a distinct flavour to the bus-stop. However, it will be effective only if the bus stops sufficiently close to the kerb

·        External aspects

o       Lighting

Well-lit bus stops are important for security purposes and identifying bus-stop

o       Bus-stop signage and flag

·        Identifying bus-stop from a distance.

Enable bus to stop close (< 6”)

Markings on the road to help driver identify and stop close to the bus-stop

o       Cleanliness

Bus-stop and surroundings should be kept clean.  A litter-bin to be placed if required.

4.      Driver training

All the above would not have the necessary impact if it is not supported by extensive driver training. Among the points the training should cover is

·        Importance of stopping at bus-stops

Ensure that drivers stop only at bus-stops and not at junctions or mid-road to pick up passengers

·        How to approach bus-stops

Important that the bus approaches the stop slowly and stops very close to the bus-stop such that the door aligns with the passenger entry.

·        Minimize time spent at bus-stop

Quick but safe entry and exit of passengers. The time saved at a bus-stop means less pile up of people and traffic, faster average speeds of the bus, thus lower travel times for passengers. If it could be calculated, there would be a significant economic value to lowering stoppage times.

 

 

5.1.4      Streetlights

 

 

Utility uses

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5.1.1      Electricity

5.1.2      Water

5.1.3      Sewerage

5.1.4      Telephone cables

5.1.5      Internet cables

5.1.6      Cable TV

5.1.7      Others

 

Requirements/specifications for each use

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Requirements of each use case will be listed comprehensively, taking inputs from multiple sources. Were possible, the requirement will be specified numerically.

Uses of streets

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There is more to a street than movement of vehicles. It also needs to be safe, usable and appealing for pedestrians, bicyclists and handicapped. It is also used for parking, turns, used by hawkers, etc. For better understanding we will classify and list these down.

4.1 People movement

4.1.1      Thoroughfare for motorized vehicles

a)      2 wheelers

b)      3 & 4 wheelers, light commercial vehicles

c)      Greater than 4 wheelers, heavy commercial vehicles.

 

4.1.2      Thoroughfare for non-motorized vehicles

a)      Pedestrians

b)      Bicyclists

 

4.1.3      Street intersections, turns and  pedestrian crossings

a)      3 intersection streets

b)      4 intersection streets

c)      Multi intersection streets

d)      Roundabouts

e)      Single turns from and into the street

f)        U-turns

g)      Standalone pedestrian crossings

 

 

 

4.2 Static uses

 

4.2.1      Parking

a)      2 wheeler parking

b)      4 wheeler private parking

c)      3 wheeler[rickshaw],Taxi and Para-transit parking

 

 

4.2.2      Hawkers

4.2.3      Bus-stops and transit facilities

4.2.4      Streetlights

 

 

4.3 Environmental functions

 

4.3.1      Trees

4.3.2      Garbage bins

4.3.3      Rain water run off

 

4.4 Utility uses

 

4.4.1      Electricity

4.4.2      Water

4.4.3      Sewerage

4.4.4      Telephone cables

4.4.5      Internet cables

4.4.6      Cable TV

4.4.7      Others