What is Hill Road? Design and Consideration Problem in 2024

Basically, a hill road is constructed in a maintained region with a cross-slope of 25% or more on road pavement. In the present generation, most of the area of the village needs suitable road pavement for better services for the maintenance areas people. this post will discuss what is hill road, design and consideration problems, special geometric design considerations, hairpin bends, etc.

What is Hill Road?

A Hill Road passes through a terrain with a cross slope of 25% or more. A hilly or mountainous area is characterized by hilly broken relief with widely differing elevations steep slopes deep garages and great a number of watercourses.

The construction of hill roads comprises various stages of work. Reconnaissance survey and track cutting formation protective and drainage work pavement work bridge.

Hill Road is the objective of engineering to establish a short easy safe and economical(SESE) route.

Why is the importance of Hill Road?

  • For the economic development of the country
  • Development of tourism in the country
  • For the industrial development in the country
  • To meet the need for strategic consideration of the country in the hilly area of the country
  • In the mountainous terrain navigation and rail traffic are not possible.
  • To establish other projects such as hydropower hill irrigation.
  • Join two or more village-to-town

What are the design and consideration problems?

Various design and consideration problems in the hill road are listed below:

  • A hilly or mountainous area is characterized by a hilly broken relief with widely differing elevations steep slope deep gorges and a greater number of watercourse complex topography the routing length ineffectively increases.
  • Due to a large number of watercourses, a large number of culvert bridges of the causeway are required when the route is to be established.
  • In mountainous terrain, it is very difficult and tedious to fix alignments topographic surveys, and other geological and hydrological analyses.
  • It is very difficult to design hairpin bends in a large number of the possibility of an accident becoming high due to the presence of hairpin bends.
  • The cost of design and construction is high
  • It’s very difficult to maintain the gradient alone the longitudinal alignment and the side distance when the route is to be constructed
  • Highway drainage management is very difficult and requires extra work. Like, catch drain vertical drain.
  • Lots of Retaining wall and Brest wall is needed when constructing the road.

What is the special geometric design consideration?

This is the initial phase of the design of the hill road. The designer should consider the following points listed below:

  • The design should be safe and efficient both during daylight and at night and also in good and bad weather.
  • The designer should have full knowledge of the condition under which the vehicle is going to operate. In the hill road, the length of the vehicle’s motor engine and gearbox system is most prominent.
  • In the case of the hill road improvement of features like grade and curvature at a later can be expensive and may sometimes be impossible.
  • The design must be complete traffic signs, signals roadside treatment, etc should provided.
  • The design should be as simple as possible from a construction point of view and from the road user
  • The maintenance cost should minimal as possible.

 Extra Consideration in Hill Road Design 

Arrangement of Hill Roads 

Choosing an arrangement in the bumpy district is a mind-boggling task. The architect should endeavor to pick a short, simple, efficient, and safe consoling course. 

General contemplations 

When planning slope streets the course is situated along valleys with sloped sides, and whenever needed over mountain passes. Because of complex geology, the length of the course is consequently expanded. Because of cruel land conditions, exceptional constructions additionally must be given. 

Aside from the exceptionally broken help which has a fixed part in deciding the arrangement and area of unique designs, climatic and geographical conditions are likewise significant. In finding the arrangement extraordinary thought ought to be made regarding the varieties in: 

  • Temperature 
  • Precipitation
  • Air pressing factor and winds 
  • Land conditions 


Air temperature in the slopes is lower than in the valley. The temperature drop is around 0.5° per 100 m of rising. 

On slants pointing toward the south and southwest snow vanishes quickly and downpour water dissipates rapidly while on inclines pointing toward the north and upper east downpour water or snow may stay for a more drawn-out time. 

Inconsistent warming of inclines, sharp temperature varieties, and disintegration by water are the reasons for slant pointing toward the south and southwest. 


Precipitation increments with expansion in ocean level. 

The most extreme precipitation is in the zone of concentrated cloud development at 1500-2500 m above ocean level. By and large, the expansion of precipitation for every 100 m of height midpoints 40 to 60 mm. 

In summer exceptionally hefty tempests may happen in the slopes and around 15 to 25% of the year may happen in solitary precipitation. The impacts of these sorts of precipitation are not kidding and ought to be viewed as well. 

Environmental pressing factors and winds 

It diminishes with expansion in rising. 

At high elevations, the breeze speeds may reach up to 25-30 m/s and the profundity of ice entrance is additionally 1.5 to 2 m. 

Concentrated enduring of rocks as a result of sharp temperature varieties which cause high breezes. 

Geographical conditions 

The tendency of folds may change from level to vertical declination of rock. These folds frequently have shortcomings. Limestone or sandstone folds might be interleaved with layers of the earth which when wetted may cause cracking along their surface. This may bring about shear or slip overlay. 

The level of strength of slope slants relies upon the kinds of rock, the level of layer tendency or plunge, the event of dirt creases, the hardness of the stones, and the presence of groundwater.

When finding the highway a designer should examine the subtleties of geographical states of that region and follow stable slope inclines where no groundwater, avalanches, and temperamental folds happen. 

Slope streets may follow diverse ways as per the achievability of the street. Nonetheless, a slope street arrangement changes for the areas along the valley base and along the mountain pass. The first is called the waterway course and the second is called the edge course.

Waterway course 

The area of a course along a waterway valley is the most regular instance of slope arrangement as there is an incredible benefit of running a street at a delicate inclination. Likewise, there is an advantage of low development costs and activity costs.

Notwithstanding, a stream valley may go through various level bends. Prerequisites for the development of enormous extensions over feeders additionally may happen. It might likewise be important to build unique holding constructions and assurance dividers on the slope side to safeguard the street against torrential slides. 

What is a Hair pin Bend?

The main part of the hill road is hairpin bends. Without hairpin bends it isn‘t possible to construct roads in hilly areas. A hairpin bend located on a hillside has the minimum slope and maximum stability.

The track cut is a narrow track o.6 to 1 meters prepared along the road alignment of the hill road to enable access for inspection during the route.

In the hill road track, the cut is done at a ruling gradient of 1 in 25. This gives a sufficient margin to obtain a rolling gradient of 1 in 20.

The designer has more than knowledge about the hairpin bends for the construction of hill roads. The hairpin bends are essential in the hill road due to the gradient of nature in the mountain area. Mainly mountain area has steep gradient so more than hairpin bends can be designed and constructed.

The following points are the most important design criteria for planning hairpin bends in the hill road.

  1. The straight length between two successive hairpin bends should be a maximum of 60 meters excluding the length of circular and transitional curves.
  2. The maximum design speed in the hairpin bends is 20kmhr
  3. The maximum radius of the inner curve of hairpin bends is 14 meters
  4. The maximum length of the transitional curve in the hairpin bends is 15 meters
  5. In the circular portion, the superelevation is 1 in 10.
  6. The maximum width of the carriageway at the apex of the curve is 11.5 meters for the two-lane pavement of the national highway
  7. The maximum width of the carriageway at the apex of the curve is 9 meters for single-lane pavement of the state highway.
  8. The maximum and minimum gradients are 1 in 40 and 1 in 200 respectively at the curve.
  9. The approach gradient shouldn’t be steeper than 5 percent for a 40-meter length road.
  10. For good visibility at the hairpin bends the island portion shall be cleared of all the trees etc.

In the mountain region may become difficult to avoid hairpin bends where the direction of the road reverses, precipitous, rock, deep valley, and obligatory points.

Some significant

The street bed ought to be found adequately above and away from the greatest water level. 

At the point when the street bed is close to the waste watercourse bank, the slant ought to be all around secured and settled. 

More consideration ought to be given to land and hydrological structures. 

The best options ought to be chosen for intersection water sources.

Edge course 

It is portrayed by the extremely steep slope. 

Countless sharp bends happen out and about with barrette twists. 

Broad earthwork is required. 

The necessity for the development of extraordinary constructions. 

The need for a long away from the air course.

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