Road Design Essay Example

Design of road

The condition of the road from Bulga to Wongalee is in a bad state that may not accommodate the current demand of 3500 vehicles in a day. Thus, this design offers realignment of the road to meet the standard requirements.

The superelevation aims at counteracting the centripetal acceleration that is created when a vehicle rounds a curve. The grade line’s profile follows the lower rail while the upper rail becomes supereleveted. A radial acceleration will occur towards the center of the curve of v2/R when the vehicle travels with radius 230m curve at constant speed of 60km/h but it is opposed by a force (W/g)(v2/R). The minimum radius of curvature for design speed of 60 Km/h:

R = V2/(127(f + e)) = 602/(127(0.15+0.15)) = 94.49m

The maximum actual super-elevation rate for a constant speed of 60 Km/h is determined by;

e = V2 / 127R – f = 602 / (127*230) – 0.15 = 0.0268m

Rounding, emax = 0.0268 = 3%

Road Design Road Design  1 L1 MRW is the minimum road width

MRW R3 R2 R1

The alignment of the center line has an impact on the cost of construction, environmental cost, and haul cost since the preliminary center line is established during the phase of reconnaissance. The alignments of the road have to be adjusted to the constraints that are imposed by terrain. The alignment adjustment horizontally assists in minimizing the potential for creating roadway sediment. The manipulation of the horizontal alignment aims at reducing the roadway cuts and fills for avoidance of the surfaces that are unstable. The steep slopes and unstable surfaces are traversed and adjusted in vertical alignment to minimize the impacts. The benches, ridge-tops, short, steep pitches assist in obtaining more stable surfaces by matching with surface treatment that may accommodate excessive wears.

Road Design  2 Shoulder Shoulder

Ditch Ditch

Traveled way



The consideration of curve widening ensures that the safety of the road is not compromised while the road shoulders are impacted by the off-tracking wheels. When the shoulders erode continuously, it turns to a source of sediments that result in weakening the road. The axles of vehicles rotate about a common center that necessitates for curve widening. The vehicle relays on the lowest curve radius and it is the highest angle of cramp and the length of the wheelbase.

The realignment of the road from Bulga to Wongalee with forest employees the vertical alignment as limiting factor. The frequent tag lines are run at the maximum attainable grades since the highest grades are provided by the configuration of vehicle, precipitation patterns, and the erosive conditions. Earth work, costs, and the damage of erosion are minimized by ensuring the center line for horizontal alignment closely follows the topography.

The equipment required for the design are; clinometers, staff compass, fiberglass tape, range rod, maps, crayons, notebook, pencils, stakes, photos, flagging, and the engineering field tables.

The road design for improvement of the road from Bulga to Wongolee aids the users with its current unworthiness. The designed re-elevated road is durable and it will assist by enhancing the safety of the vehicles using the road. There is minimum cost incurred in maintaining the designed road and offers easy maneuvering of vehicles on it.


Armstrong L., A Method of Measuring Road Surface Wear. (2007). Print. P. 27 – 32.

Reid M. & Dunne T. Sediment Production from Forest Road Surfaces, Water resources research.

(2000). Print.