Cork Institute of Technology
Bachelor of Engineering in Civil Engineering –Award
(Time: 3 Hours)
Instructions: All questions carry equal marks
Answer five (5) Questions – candidates must
attempt all questions in SECTION A and any
two (2) questions from SECTION B
Attachments: (i) Table 3 from NRA TD9/00 (Road
Geometry Handbook) (ii)graphs from LR1132
Examiner: Mr. D.J.Walsh
Mr. P. Moran
Mr. J Lapthorne
Mr. J. Kindregan
Question 1 – where appropriate NRA Road Geometry Handbook standards to apply
(i) Which road classifications in the Irish road network come under the remit of the NRA?
(ii) Alignment Constraint (Ac) and Layout Constraint (Lc) are two factors used in the
assessment of what?
(iii) A single carriageway road is to have a Design Speed of 100km/hr.
What are the critical sight distances to be satisfied when designing the road?
(iv) What is meant by the terms (i) Relaxation (ii) Departure from design standards?
(v) Use a neat sketch to illustrate the geometrical cross-sectional details of a Standard
Single Carriageway. Dimension the key features of the cross section.
(vi) Cutback Bitumen and Bitumen Emulsion represent an alternative to the traditional
Penetration Grade Bitumen binder – how are they produced and what advantage do
they offer over the traditional Penetration Grade Bitumen?
(vii) The use of a Road Tar binder in-lieu of a Petroleum Bitumen Binder can be
advantageous in certain circumstances – what advantages does Road Tar offer over
Petroleum Bitumen? What are its two major disadvantages?
(viii) Which document specifies the geometric design standards required of highway
markings and signing? (Q1: 8 parts @ 2.5 marks each – 20Marks)
The minimum distance required for safe passing on two-lane single carriageway
roads, i.e. the Full Overtaking Sight Distance (FOSD), has four distinct
component elements - Fig. Q2 refers.
The overtaking vehicle travels a distance d1 during the perception/ reaction time and a
distance d2 while completing the overtaking manoeuvre – this vehicle is assumed to
accelerate from an initial speed two steps below the design speed of the road to a final
speed equal to the design speed v at the completion of the overtaking manoeuvre – the
acceleration a occurs over the total distance (d1+d2) and is completed in a time t
(Note that the design speed steps are related by a factor of 21/4)
The vehicle travelling in the opposite direction travels a closing distance d4 during this
A safety distance d3 is provided between the vehicles on completion of the manoeuvre.
(i) Assuming a safety distance equal to 20% of the closing distance show that the Full
Overtaking Sight Distance may be calculated as
FOSD = d1+d2+d3+d4 = 2.05vt
v is the design speed of the road and
t is the time taken by the overtaking vehicle to travel the reaction & overtaking
(ii) An assumption that 85% of overtaking manoeuvres are completed in a time t of 10
seconds has been used to generate the FOSD values specified in Table 3 of the NRA
Road Geometry Handbook – verify this by comparing the FOSD value obtained using
the equation derived in (i) above with the value in Table 3 for a design speed of
100km/hr. (3 marks)
(iii) (a) Illustrate how the available FOSD is measured for a given vertical road alignment
– clearly show the envelope of visibility and the relevant heights involved.
(b) Explain why FOSD is not of concern to the road designer for dual carriageways.
(The following equations of physics may be of assistance; v = u+at and s=ut+0.5at2 )