1. Elements of a Typical Cross-section of Road and Highway drainage
Transportation Engineering – I
Dr. Attaullah Shah

2. Road
A way or path over which cyclists, vehicles and pedestrians can pass lawfully.
Roads are normally used for transportation within a country.

3. Advantages of Roads
Nearest to the man, as for going to airport, harbor or railway station.
Can be used by all types of vehicles from cycles to trailers.
Can lead to any remote area and road users have freedom of movement.
Vehicle movements are not time bound, roads are open to traffic for 24 hours.

4. Typical Road Cross-Section

5. Typical Road Cross-Section

6. Cross-Section Elements
The cross section of a road includes some or all of the following elements:
Traveled way
Roadway
Median
Shoulder
Kerb
Traffic Barriers
Bicycle and pedestrian facilities
Drainage channels and side slopes

7. Two Lane Rural Highway Cross-Section

8. Urban Highway Cross-Section

9. Selection of appropriate cross-section elements
In selecting the appropriate cross-section elements and dimensions, designers need to consider a number of factors:
Volume and composition (percent trucks, buses, and recreational vehicles) of the vehicular traffic expected to use the facility
The likelihood that cyclists and pedestrians will use the route
Climatic conditions

10. Selection of appropriate cross-section elements
The presence of natural or human made obstructions adjacent to the roadway (e.g., rock cliffs, large trees, wetlands, buildings, power lines)
Type and intensity of development along the section of the highway facility that is being designed
Safety of the users
The most appropriate design is the one that balances the mobility needs of the people using the facility (motorists, pedestrians, or cyclists) with the physical constraints of the corridor within which the facility is located.

11. Right of Way
The right of way can be described generally as the publicly owned area of land that encompasses all the various cross-section elements.
The right of way is the land set aside for use as a highway corridor.
Rights of way are purchased prior to the construction of a new road, and usually enough extra land is purchased.
Sometimes, rights of way are left vacant after the initial roadway facility is constructed to allow for future highway expansion.

12. Right of Way Requirements of area for right of way are as follows:
For 2 lane road = 150 ft width of area
For 4 lane road = 250 ft width of area
For 8 lane road = 300 ft width of area

13. Traveled Way or Carriage Way
The portion of the roadway provided for the movement of vehicles, exclusive of shoulders.
Number of lanes on a traveled way are decided on the basis of expected traffic volumes and appropriate level of service required for the facility.

14. Traveled Way or Carriage Way
Lane width strongly influences traffic safety and comfort
Lane width ranges from m with 3.6 m lane predominant on high-type highways
Two-lane two-way highways with the 3.6 m lane provide safe clearance between large commercial vehicles

15. Dual Carriage Way
When traffic volumes are quite heavy, carriageway may be divided into two parts by providing a median strip and each portion of the carriage way is reserved for traffic moving in opposite direction.

16. Road Way The portion of a highway provided for vehicular use.
It includes both carriageway and shoulders.

17. Formation Width
It is the sum of widths of carriage way, shoulders and median strips if provided.
In case of embankments, it is measured as the top width.
In case of cutting, it is the bottom width of the cutting from which side drains are excluded.

18. Shoulders
Shoulders are the strips provided on both sides of the carriage way.

19. Functions of shoulders
accommodation of stopped vehicles (disabled vehicles, bus stops)
emergency use
lateral support for the pavement
space for roadside facilities
space for bicycles and pedestrians
driving comfort (freedom from strain)
improvement in sight distance
improvement in capacity

20. Width of shoulders
Low-type roads -- minimum 0.6 m, recommended m
Shoulder provided for bicycles -- minimum 1.2 m wide
High-type roads -- minimum 3.0 m, recommended 3.6 m
Shoulders should be continuous.
Shoulders on bridges should have the same width as on the approach sections.

21. Median or Traffic Separators
It is the physical or painted separation provided on divided highways between two adjacent roadways.
Medians can also be used to isolate slow and fast moving traffic in the same direction.
Width of medians ranges from
1.2 to 24 m.

24. Median

25. Function of medians separate opposing traffic
recovery area for out-of-control vehicles
stopping area
storage of right-turning and U-turning vehicles
minimize headlight glare
provision for future lanes

26. Kerb
It is the dividing line between carriageway and footpath.

27. Functions of Kerbs drainage control roadway edge delineation
right-of-way reduction
delineation of pedestrian walkways
reduction in maintenance operation
Assistance in roadside development

28. Types of Kerbs Class I Kerb: Height 7-9 cms
Class II Kerb: Height cms
Barrier: cms
Submerged: provide lateral stability

29. Foot Path or side Walk Foot paths are provided in Urban roads
These are raised strips constructed along both the edges of roads.
Their minimum recommended width is 1.3 m.

30. Foot Path or side Walk

31. Foot Path or side Walk

32. Bicycle and Parking lane
Bicycle lane is a portion of the roadway designated by striping, signing, and/or pavement markings for preferential or exclusive use by bicycles and/or other non-motorized vehicles.
Parking lane is an additional lane provided on Urban roads and streets for on-street parking.

33. Bicycle and Parking lane
Minimum Width Requirements

34. Bicycle and Parking lane

35. Traffic Barriers
A longitudinal barrier, including bridge rail, or an impact attenuator used to
Redirect vehicles from hazards located within an established Design Clear Zone
To prevent median crossovers
To prevent errant vehicles from going over the side of a bridge structure
To protect workers (occasionally)
To protect pedestrians, or bicyclists from vehicular traffic

36. Traffic Barriers

37. Traffic Barriers

38. Drainage Channels and Side slopes
Drainage channels and side slopes are provided along the length of road for storm water drainage etc.

39. Drainage Channels and Side slopes
Drainage channels should:
have adequate capacity for the design runoff,
minimize damage to the highway caused by unusual storm water,
minimize risk for motorists,
be resistant to the high speed water flows where expected,
prevent sedimentation of the particles carried by water.

40. Drainage Channels and Side slopes
Side slopes should
insure the stability of the roadway
provide opportunity for recovery of an out-of-control vehicle

41. Transportation Engineering - I
Part 2 Highway Drainage
Transportation Engineering - I

42. Highway Drainage
A means by which surface water is removed from pavement and ROW
Redirects water into appropriately designed channels
Eventually discharges into natural water systems

43. Inadequate Drainage Damage to highway structures Loss of capacity
Visibility problems with spray and retro-reflectivity
Safety problems, reduced friction and hydroplaning

44. Highway Drainage Transverse slopes Longitudinal slopes
Removes water from pavement surface
Facilitated by cross-section elements (cross-slope, shoulder slope)
Longitudinal slopes
Minimum gradient to maintain adequate slope in longitudinal channels
Longitudinal channels
Ditches along side of road to collect surface water after run-off

45. Transverse slope

46. Longitudinal slope

47. Longitudinal channel

48. Drainage System Three phases
To Estimate the quantity of water to reach the system
Hydraulic design of system elements
Comparison of different materials to serve the purpose
Steep slopes provide good hydraulic capacity and lower ROW costs, but reduces safety and increases erosion and maintenance costs

49. Hydrologic Analysis Q = CIA (english) or Q = 0.0028CIA (metric)
Q = runoff (ft3/sec) or (m3/sec)
C = coefficient representing ratio or runoff to rainfall
I = intensity of rainfall (in/hour or mm/hour)
A = drainage area (acres or hectares)

50. Transverse Slope
Undivided traveled ways (two- and multilane) on tangents and flat curves have a crown in the middle and slope downward toward both edges (camber). The downward cross slope may be a plane or rounded section (parabolic), or a combination of the two.
One-way traveled ways on divided highways may be crowned separately or may have a unidirectional cross slope/cross fall.

51. Transverse Slope

52. Transverse Slope

53. Transverse Slope

54. Crowns vs. Unidirectional Slopes
Type of Roadway
Pros
Cons
Crowned separately
rapid drainage during rainstorms
difference between low and high points is minimal
inlets and underground drainage (drainage towards the median)
difficult design of at-grade intersection elevation
use of such sections should be limited to regions with high rainfall
Unidirectional cross slopes
more comfortable for drivers changing lanes
drainage away from the median saves inlets and drains
simplifies treatment of intersections
drainage is slower
difference between low and high points of the cross section is larger

55. Cross Slopes on Tangents
Contradictory design controls
A steep lateral slope reduces water ponding and the width of the water flow along the curb.
A flat lateral slope reduces vehicles' drift towards the low edge.
Recommended design controls
Lateral drift of vehicles at high speed is barely perceptible on cross slopes up to 2%. The slope of % is acceptable on high-speed highways. In the areas of intense rainfall a maximum cross slope is 2.5%.
Crown section
Change in the cross slope of 3-4% causes swaying of high body vehicles. Rounded crowns reduce discomfort.

56. Curbed Highways
The minimum slop values of % in areas with intense rainfalls will cause wide sheet of water on the curbed traveled way.
Possible improvements:
parabolic cross section with increasing cross slope towards the outer edges,
gutter along the curb with the cross slope larger than on the traveled way,
on multilane traveled way, cross slope broken along traffic lane edges, increasing from the minimum value on the innermost lane up to the maximum value on the outermost lane. This solution is used on uncurbed sections as well.

58. Drainage Channels and Sideslopes
Design considerations of highway drainage includes
safety
good appearance
control of pollutants
economy in maintenance
This can be achieved by applying
flat side slopes
wide drainage channels
rounding

59. Drainage Channels Types of Drainage Channels
800
802
Roadside channel
Flume
804
814
Intercepting channel
806
Toe-of-slope channel
812
794
810
808
798
800
802
804
806
808

60. Drainage Channels Drainage channels should:
have adequate capacity for the design runoff,
minimize damage to the highway caused by unusual storm water,
minimize risk for motorists,
be resistant to the high speed water flows where expected,
prevent sedimentation of the particles carried by water.

61. Side slopes Side slopes should: insure the stability of the roadway
provide opportunity for recovery of an out-of-control vehicles

62. Roadside Channels
Steep sides improve hydraulic efficiency and reduce right of way costs
Flatter sides improve slope stability and traffic safety, reduce maintenance costs
Side slopes 1:4 or flatter provides a good chance of recovery for errant vehicles and relax drivers' tension (roadside channel is visible to drivers)
Side slopes of 1:5 or 1:6 are recommended in the flat areas
Intercepting channels have a flat cross section form by a dike made with borrow material
Median drainage channels are shallow depressed areas with inlets
Flumes are open channels or pipes used to connect intercepting channels or shoulder curbs with roadside channels
Channel lining prevents channels erosion caused by fast stream of water.
Examples: grass (where possible), concrete, stone etc.

63. Side slopes Safety consideration
Rounded hinge point reduces the chance of an errant vehicle becoming airborne
Fore slopes 1:6 or flatter can be negotiated by errant vehicles
Fore slopes 1:3 with liberal rounding provide a good chance for recovery
Slopes steeper than 1:3 can be used only where justified by local conditions. The use of roadside barriers should be considered
Maintenance consideration
Flat and well-rounded side slopes simplify establishment of turf and its maintenance
Slopes 1:3 or flatter enable the use of motorized equipment

64. Side slopes Other rules
Flat, well-rounded side slopes create a streamlined cross section. Advantages for the streamlined cross sections are:
natural, pleasant appearance,
improved traffic safety,
snow drift prevented,
easy maintenance.
Retaining walls should be considered where slopes would be steeper than 1:2.
Standard slope for rock cuts is 2:1. In good-quality rock, slopes ranges from 6:1.

65. Sideslopes