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In architecture, parking and turning radius refer to the amount of space required for a vehicle to park or make a turn within a certain area. The parking radius is the minimum amount of space required for a vehicle to park, including space for doors to open, while the turning radius is the minimum amount of space needed for a vehicle to make a turn.

These are important considerations in the design of parking lots, driveways, and other vehicular areas to ensure that vehicles can maneuver safely and comfortably.

Introduction

• The growing population of India has created many problems – one of the challenging ones being car parking which we confront almost every day.

• Parking spaces are usually outlined by 12-20mm wide yellow or white painted lines.
• When parking is facing a wall, these lines are often painted at a height of up to 1 m for better visibility.
• Guide rails in the floor along the side have also proved popular for demarcation of parking limits, and can be about 50-60cm long, 20cm wide and 10 cm high.
• Where vehicles are parked in lines facing walls or at the edge of the parking deck in a multi-Storey carpark, it is common practice to provide buffers, restraining bars or railings up to axle height to prevent cars from going over the edge.
• Where cars are parked face to face, transverse barriers about 10cm high can be used to act as frontal stops. 

1) Type of parking

i) On street parking

• On street parking means the vehicles are parked on the sides of the street itself.
• This will be usually controlled by government agencies itself. Common types of on-street parking are as listed below.
• As per IRC (Internet Relay Chat) the standard dimension of a car is taken as 5× 2.5 m and that for a truck is 3.75× 7.5 m.

ii) Off street parking

• Off street parking means vehicles are parked off the street itself. This will be usually controlled by commercial agencies itself.

iii) Parallel parking

• The vehicles are parked along the length of the road.
• Here there is no backward movement involved while parking or un parking the vehicle.
• Hence, it is the most safest parking from the accident perspective.
• However, it consumes the maximum curb length and therefore only a minimum number of vehicles can be parked for a given kerbed length.
• This method of parking produces least obstruction to the on-going track on the road since least road width is used.

iv) 30-degree parking

• In thirty-degree parking, the vehicles are parked at 30 with respect to the ruined alignment.
• In this case, more vehicles can be parked compared to parallel parking.
• Also, there is better maneuver-ability.
• Delay caused to the track is also minimum in this type of parking.

v) 45-degree parking

• As the angle of parking increases, more number of vehicles can be parked.
• Hence compared to parallel parking and thirty-degree parking, more number of vehicles can be accommodated in this type of parking.

vi) 60-degree parking

• The vehicles are parked at 60 to the direction of road.
• More number of vehicles can be accommodated in this parking type.

vii) Right angle parking

• In right angle parking or 90 parking, the vehicles are parked perpendicular to the direction of the road.
• Although it consumes maximum width kerbed length required is very little.
• In this type of parking, the vehicles need complex maneuvering and this may cause severe accidents.
• This arrangement causes obstruction to the road track particularly if the road width is less.
• However, it can accommodate maximum number of vehicles for a given kerbed length.

2) Turning path

• The turning radius, or turning path, of a vehicle is the smallest circular turn that it can make.
• Turning circles are used to evaluate how easily a specific car can make a U-turn or park.

• The type, size and shape of a turning place in a road depends on the road use in that particular area.
• It also has to be suitable for the needs of the road users and must meet town planning requirements.
• It is difficult to make recommendations for a correct choice of road turning place which is valid in all cases.
• The interests of the fire and refuse collection services have to be taken into account in deciding on road turning places.
• Many authorities refuse to service areas with dead-end roads or lanes, where refuse collection lorries can turn only by manoeuvring backwards and forwards or must reverse quite a long distance.
• Road turning places can be designed as hammerheads, Turning, circles or loops as shown in the figure below.

• The hammerhead type turning place calls for backwards and forwards manoeuvring.
• Turning circles and loops are preferable, as motor vehicles can drive straight round them without having to stop.
• To facilitate steering, road turning places should be arranged asymmetrically on the left, or on the right in the case of those countries like the UK which drive on the left-hand side of the road as shown in the figure above.

• Adequate clear areas should be left along the outside edges of the turning areas to safeguard fixed obstructions from the overhang of turning vehicles.
• In the case of turning loops, the central area to be driven around can be planted as shown in the figure.

• Hammerhead turning places are really only suitable for cars.
• They are not required for carriageways over 6m wide, if garage forecourts or footpath crossings are available for turning purposes.

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Proper design of parking and turning areas can improve the flow of traffic, reduce the risk of accidents, and ensure compliance with regulations.

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