Road Patterns
1.Rectangular or Block pattern: In this pattern, the whole area is divided into rectangular blocks of plots, with streets intersecting at right angles. The main road which passes through the center of the area should be sufficiently wide and other branch roads may be comparatively narrow. The main road is provided a direct approach to outside the city.
Advantages:
1. The rectangular plots may be further divided into small rectangular blocks for construction of buildings placed back to back, having roads on their front.
2. In this pattern has been adopted for the city roads.
3. The construction and maintenance of roads of this pattern is comparatively easier.
Limitations:
1. This pattern is not very much convenient because at the intersections, the vehicles face each other. Example: Chandigarh has rectangular pattern.
2.Radial or Star and block Pattern: In this pattern, the entire area is divided into a network of roads radiating from the business outwardly. In between radiating main roads, the built-up area may be planned with rectangular block.
Advantage
1. Reduces level of congestion at the primary bottleneck location.
2. Prevents traffic from accessing local flow routes in the direction of the event venue that operate in favor of egress traffic flow.
3. If one is block then other side traffic can move.
4. Vehicles face each other less than block pattern.
Limitations
1. Proves particularly effective if two-lane ramp traffic does not have to merge at downstream end of ramp.
2. Safety appurtenances such as guide rail transitions, crash attenuators, and post support bases have not been designed to provide adequate protection at hazardous locations from the opposite direction of travel
3.Radial or Star and Circular Pattern: In this system, the main radial roads radiating from central business area are connected together with concentric roads. In these areas, boundary by adjacent radial roads and corresponding circular roads, the built-up area is planned with a curved block system.
Advantages
1. At traditional intersections with stop signs or traffic signals, some of the most common types of crashes are right-angle, left-turn, and head-on collisions. These types of collisions can be severe because vehicles may be traveling through the intersection at high speeds. With circular pattern, these types of potentially serious crashes essentially are eliminated because vehicles travel in the same direction.
2. Installing circular pattern in place of traffic signals can also reduce the likelihood of rearend crashes.
3. Removing the reason for drivers to speed up as they approach green lights and by reducing abrupt stops at red lights.
4. Because roundabouts improve the efficiency of traffic flow, they also reduce vehicle emissions and fuel consumption.
Limitations:
1. Center lines of roads leading to circular pattern should be properly aligned with the central island.
2. Approach roads should be sufficiently curved, far enough in advance of circular pattern, to reduce vehicle speeds of entering drivers.
3. Islands separating the approach and exit lanes, known as splitter islands, should extend far enough to provide pedestrian refuge and to delineate the roundabout.
4. Traffic signs, pavement markings, and lighting should be adequate so that drivers are aware that they are approaching a roundabout and that they should reduce their travel speed.
5. For older drivers declines in vision, hearing, and cognitive functions, as well as physical impairments, may affect some older adults' driving ability. Intersections can be especially challenging for older drivers.
4.Radial or Star and Grid Pattern: Change in direction, and because street patterns are the most enduring physical element of any layout, it could potentially contribute to systematic site planning and, consequently, deserves a closer look. Though the network is entirely interconnected, north-south movement becomes circuitous, indirect, and inconvenient, making driving an unlikely choice and vividly illustrating that interconnectedness by itself is insufficient to facilitate movement.
Advantages:
1. Keep vehicular traffic safe with a high proportion of 3-way intersections.
2. Reduce cut-through traffic by similar or other means.
3. Improve traffic flow in both directions using Savannah‟s cellular structure.
4. Improve land use efficiency and unit density.
Limitations:
1. Islands separating the approach and exit lanes, known as splitter islands, should extend far enough.
2. Traffic signs, pavement markings, and lighting should be adequate so that drivers are aware that they should reduce their travel speed.
Examples: The Nagpur road plan formulae were prepared on the assumption of Grid pattern.
5. Hexagonal Pattern: In this pattern, the entire area is provided with a network of roads formatting hexagonal figures. At each corner of the hexagon, three roads meet the built-up area boundary by the sides of the hexagons is further divided in suitable sizes.
Advantages:
1.Three roads meet the built-up area boundary by the sides of the hexagons.
Limitation:
1.Traffic signs, pavement markings, and lighting should be adequate so that drivers are aware that they should reduce their travel speed.
6.Minimum Travel Pattern: In this road pattern, city is contented by sector center, suburban center and neighborhood center by the road which required minimum to connect the city center.
Advantages:
1.These types of potentially serious crashes essentially are eliminated.
Limitations:
1. Traffic signs, pavement markings, and lighting should be adequate so that drivers are aware that they should reduce their travel speed.
2. Intersections can be especially challenging for older drivers.
Planning Surveys
The field surveys thus required for collecting the factual data may be called as planning survey or fact finding surveys:
Highway planning phase includes
i) Assessment of road length requirement for an area
ii) Preparation of Master plan showing the phasing of plan in annual and or five year plans.
The planning surveys consists of the following studies
i) Economical Studies
ii) Financial studies
iii) Traffic or road use studies
iv) Engineering studies.
Objective of Planning Surveys
1.Workout, the financial system and recommended changes in tax arrangements and budget procedures, provide efficient, safe economics, comfortable and speedy movement for goods and people.
2.Plan a road network for efficient traffic operation at minimum cost.
3.Plan for future requirements and improvements of roads in view of developments and social needs.
4.Fix up data wise priorities for development of each road link based on their utilities.
Preparation of Plans
Interpretation of Planning Surveys
i) To arrive at the road network with maximum utility among alternative proposals.
ii) To fix up the priority of the construction projects and phase the development plan
iii) To assess the actual road use by studying traffic flow patterns.
iv) Based on the studies, structural and geometric features are constructed.
v) Comparisons of the areas may be obtained on the basis of their economic activities.
vi) On statistical basic, the data obtained in fact finding surveys may be analyzed for the future trends in development of an area.
Master Plan
Master plan is referred to as road development plan of a city; district or a street or for whole country. It is an ideal plan showing full development of the area at some future date. It serves as the guide for the plan to improve some of the existing roads and to plan the network of new roads.
It helps in controlling the industrial, commercial and agricultural and habitat growth in a systematic way of that area.
It gives a perceptive picture of a fully developed area in a plan and scientific way.
Stages in the Prepartion of Master Plan
1.Data Collection: It includes data regarding existing land use, industrial and agricultural growth, population, traffic flow, topography, future trends.
2.Preparation of draft plan and invite suggestions and comments from public and experts.
3.Revision of draft plan in view of the discussions and comments from experts and public.
4.Comparison of various alternate proposals of road system and finding out the sequence in which the master plan will be implemented.
In India targeted road lengths were fixed in various road plans, based on population, area and agricultural and industrial products. The same way it may be taken as a guide to decide the total length of road system in each alternate proposal while preparing a master plan for a town or locality.
