Transportation Engineering Assignment: Highway Design and Transition Curve

Highway Design for Heavy Traffic Volume

You are expected to answer to the questions provided in the following assignment. The assignment must be written/typed (e.g., using MS Word) as the answer to the questions. Any hand-written-note will not be assessed. Note that size of your answers is at your discretion but no more than 5 pages for all answers. Other materials more than 5 pages (e.g., supporting documents, calculations, or other figures/tables) can be placed in the appendix, where required. You can support your answers by evidencebased analysis and synthesis of issues raised in the assignment task. You can also analyse the data by means of graphs and tables in MS Excel software.

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A divided rural multilane highway is required to cope with an AADT of 35 000 veh/day. A 60 mi/h design speed is chosen with lanes of a standard 3.65 m width and obstructions within 0.61 m on both sides of roadway. The terrain is mountainous and the percentages for the various heavy vehicle types are as follows: PT = 6%, PB = 4% and PR = 7%. The Driver Population is “Ideal”. The Peak Hour Factor (PHF) is 0.85 and the Directional Factor D is estimated at 0.65.

If the highway is required to maintain LOS C and it is to be designed to cope with the 30th highest hourly volume during the year, calculate the followings:

 If the client requires a reduction of 1 lane per direction, demonstrate what is the best solution to adopt amongst the followings:

1. a) extending the “Distance to obstruction from travelled edge” up to 1.83 m;
2. b) rearranging the whole highway over a type of terrain from “rolling” to “level”.
3. c) designing to cope with the highest hourly volume during the year.

Critically discuss and prove by calculation-based evidence any potential solution(s) other than those at point 1.2, that may reduce the number of lanes for the concerning highway (hint: keep constant the following parameters: divided multi-lane arrangement; AADT = 30000 veh/day; Design Speed = 60 mi/h; lane width = 3.65 m; “ideal” driver population; PHF = 0.85; D = 0.65).

A transition curve is required for a single carriageway road with a design speed vdesign = 23.61 m/s. The bearings of the two concerning straights are 20° and 59°. Assuming a value of 0.45 m/s3 for C and a superelevation e = 7.0%, calculate the followings (clearly reference the concerning ruling equations and provide step-by-step calculations and drawings, where required):

The transition length, L.

The shift, S.

The length along the tangent required from the intersection point to the start of the transition, IT? .

The form of the cubic parabola and the coordinates of the point at which the transition becomes the circular arc of radius R.

Plot the transition curve assuming a proper offset for the largest x or y coordinate.

The optimum value of “rate of change of radial acceleration” Copt that meets the criterion L ≤ Lmax with the least difference (L = length of the transition curve; Lmax = maximum length of transition curve recommended by the UK Standards)? (round up Copt to the 2nd decimal digit).