For any built environment, circulation is a vital aspect of design. Designing the pathways, and having different levels of circulation to separate the pedestrian and vehicular traffic, is important for a holistic design. 

In the days of horse-drawn carriages and vintage cars, streets were designed with cobblestones and were meant more for pedestrians. As trams and buses entered the streets, the streets were widened and a separate pedestrian footpath was designed at the edges. 

The modern traffic levels and the multiple usages of streets have resulted in various levels of circulation such as highways, and city-level streets, all the way down to a simple pedestrian footpath. 

Streets

Hierarchy of Roads in Urban Planning

• Arterial Roads
  • These are the roads at the top of the hierarchy 
  • They carry the maximum volume of traffic 
  • They are characterized by the visible segregation of the different directions of traffic movement
  • The roads are usually 50-80m and allow speeds of 50-60 km/h and below
• Sub-Arterial Roads
  • These roads function similarly to arterial roads, but in areas where access is constrained
  • The roads are usually 30-50m and allow speeds of 50 km/h and below
• Distributor/Collector Roads 
  • They connect the arterial and sub-arterial roads with the access roads
  • There is moderate traffic compared with arterial roads
  • The roads are usually 12-30m and allow speeds of 30km/h and below
• Access Roads
  • They have the lowest traffic capacity
  • They are present in localities and used to divide a locality into its layouts
  • The roads are usually 15-30m and allow speeds of 15-30km/h and below
  • They are characterized by their ability to provide access to an individual building

Design of Streets

1. Street Elements
   • Footpaths
     • The width and height of footpaths should conform to the universal accessibility standards
     • The materials used for footpaths should be tough and anti-skid
     • There should be drainage provided for rainwater to be cleared off the surface 
     • There should be no obstructions such as signage, vehicular traffic, furniture, and vegetation.
     • If the pathway is along the entrance to a property or at junctions, an appropriate slope should be provided for smooth transitions onto the road and back onto the pavement.

• Bus Lanes
  • A separate bus lane should be provided on roads
  • This lane should be closest to the pavement, and bus stops
  • The lane can be separated by providing visual segregation or a height difference.

• Parking
  • The on-street parking should be done in a way that does not interfere with pedestrian movement
  • Curbsides and intersections should be devoid of parking 
  • Parking should not be provided near bus stops
  • A designated space that is indented away from the traffic

2. Safety Elements
   • Pedestrian crossings 
     • Signaled pedestrian crossings should be provided at junctions
     • The pathway should be defined by zebra crossings
     • The space between the “STOP” line and crossing should be 2m
     • Tactile paving should be incorporated for the visually impaired

• Median and Dividers
  • Medians must be placed in the middle of the road to divert the two directions of traffic
  • The median must be visible to the driver from their seating position
  • The dividers must be temporarily fixed, and removable in case of maintenance or emergencies

• Street Furniture and Lighting
  • Seating, trashbin, railings, and signages fall under street furniture
  • The seating and railings should follow anthropometric standards
  • Seating should be provided under shaded areas
  • Traffic signs and other signages must be prominent, and visible to both pedestrians and vehicular traffic
  • Street lighting should be diffused and placed at a great height to ensure maximum reach and visibility, without compromising visual comfort

3. Multi-Utility Elements
   • Plantation
     • Plantations on streets are used for the design, functional and aesthetic aspects
     • They are used for providing shade to the pedestrians
     • They improve air quality 
     • They reduce ambient heat and surface drain-off
     • The greenery makes a street look aesthetic

• Storm Water Management
  • Stormwater is collected by an inlet at the edge of the carriageway (path meant for vehicular traffic)
  • The water is then transported through pipes to catchment areas
  • The natural drainage of water should be enabled by the street design
  • The footpath should have a gradient slope towards the shoulder of the street
  • Paver blocks and bioswales can help in providing drainage through pores that connect to the soil or pipes

• Public Toilets
  • Public toilets are an essential aspect of street design 
  • The toilets should be designed such that the foul smell is redirected away from the street 
  • The transition and access from the street and toilet should be easy and efficient

These simple points and tips, when implemented efficiently, can drastically improve a built environment. It is key that the design is universally accessible, the circulation aids in decongestion, and there is aesthetic value.