UNIVERSITY OF SOUTH AFRICA
College of Science, Engineering and Technology
⋄ ⋄ ⋄ ⋄ ⋄ ⋄ ⋄ ⋄ ⋄⋄
TRANSPORTATION ENGINEERING,
PAVEMENT & GEOMETRIC DESIGN
Assignment 01 — 2026
⋄ ⋄ ⋄ ⋄ ⋄ ⋄ ⋄ ⋄ ⋄⋄
TPG3700
Module:
01
Assignment :
A, B, C, D, E, F, G, H, I, J
Questions Covered:
100
Total Marks:
2026
Year:
Transportation Engineering Examination — Detailed Solutions
,UNISA | Transportation Engineering Exam Answers
Contents
1 Question A: Road Classification and Design 4
1.1 A.1 TRH26 Classification of a U5b Road and TRH4 Equivalent . . . . . 4
1.2 A.2 Design Hourly Volume for the Year 2036 . . . . . . . . . . . . . . . . 5
1.3 A.3 Four-Lane Divided Highway Cross-Section . . . . . . . . . . . . . . . . 7
1.3.1 A.3.1 River Basin Maps and Highway Location . . . . . . . . . . . . . . . 7
1.3.2 A.3.2 Carriageway Width and Travelled Way Width . . . . . . . . . . . . 8
2 Question B: Traffic Signals 9
2.1 B.1 Traffic Signal Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.1.1 B.1.1 Signal Phase and Signal Cycle . . . . . . . . . . . . . . . . . . . . . 9
2.1.2 B.1.2 Pre-Timed and Demand-Actuated Traffic Signals . . . . . . . . . . . 9
2.2 B.2 Pre-Timed Intersection – Green Interval Calculation . . . . . . . . . 10
3 Question C: Stopping Sight Distance 14
3.1 C.1 Perception-Reaction Time . . . . . . . . . . . . . . . . . . . . . . . . . . 14
3.2 C.2 Brake Force Coefficient from TRH17 . . . . . . . . . . . . . . . . . . . 14
3.3 C.3 Minimum SSD on a Flat (Levelled) Road Section . . . . . . . . . . . 15
3.4 C.4 SSD on a Road Section with 5% Gradient . . . . . . . . . . . . . . . . 16
3.5 C.5 Comparison with TRH17 Recommended Values . . . . . . . . . . . . 16
4 Question D: Superelevation and Circular Curve Verification 18
5 Question E: Horizontal Curve Geometry 20
5.1 E.1 Curve Central Angle, Length, and Deflection Angle at 1+038.491 . 20
5.2 E.2 Total Widening Requirement for Articulated Bus . . . . . . . . . . . 21
5.3 E.3 Sight Distance Check for Building 15 m from Edge of Road . . . . . 22
Page 2 of 39
,UNISA | Transportation Engineering Exam Answers
6 Question F: Superelevation Transition 24
6.1 F.1 Transition Stations (Points of Change) . . . . . . . . . . . . . . . . . . 24
6.2 F.2 Length of Fully Superelevated Circular Curve . . . . . . . . . . . . . . 25
6.3 F.3 Superelevation Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
7 Question G: Vertical Alignment – Sag Curve 27
7.1 G.1 Chainages and Elevations of BVC, EVC, and Lowest Point . . . . . 27
7.2 G.2 Minimum Curve Length per TRH17 Rate of Vertical Curvature . . 29
7.3 G.3 Curve Length Safety Check for Minimum SSD = 149 m . . . . . . . 29
7.4 G.4 Drainage Requirements and Minimum Grade . . . . . . . . . . . . . . 30
8 Question H: Subgrade CBR Analysis and TRH4 Design 31
9 Question I: Equivalent E80 Calculations 34
9.1 I.1 Equivalent Daily E80s from Axle Load Count . . . . . . . . . . . . . . 34
9.2 I.2 Pavement Class (ES) for New 4-Lane Divided Road . . . . . . . . . . 36
10 Question J: TRH4 Pavement Structure Design 38
10.1 J.1 All Possible Alternative Pavement Structures from TRH4 . . . . . . 38
10.2 J.2 Neat Sketches of Alternative Pavement Structures . . . . . . . . . . . 39
Page 3 of 39
,UNISA | Transportation Engineering Exam Answers
Question A: Road Classification and Design
A.1 TRH26 Classification of a U5b Road and TRH4 Equivalent
Question: Use TRH26 guidelines to classify a U5b road. Also provide the closest equivalent
class given in TRH4.
TRH26 Classification of U5b:
Under the TRH26 framework, roads are classified by function, land use context, and traffic
volumes. A U5b road falls within the urban road hierarchy as follows:
• Category U: Urban road network
• Level 5: Local access road serving residential land uses at the lowest functional level
• Sub-class b: Low volume, primarily serving pedestrians and slow-moving vehicles, with
traffic volumes typically below 500 vehicles per day (vpd)
A U5b road is a minor local street or access road within a residential area. It has minimal
through-traffic, low posted speeds (generally 30–40 km/h), and its primary role is to provide
direct property access rather than to carry through-traffic.
Closest TRH4 Equivalent:
TRH4 classifies roads by category based on traffic loading (equivalent 80 kN single-axle loads,
E80s) and environmental conditions. The closest equivalent to a U5b road in TRH4 is:
Key Distinction
TRH4 Category: ES1 or ES2 (low-volume pavement category). U5b roads carry
very low traffic and therefore require only light pavement design, corresponding to the
lowest TRH4 traffic loading class.
Table 1: TRH26 vs TRH4 Road Class Comparison
Aspect TRH26 (U5b) TRH4 Equivalent
Function Local access Low-volume pavement
Volume Below 500 vpd ES1/ES2 class
Speed 30–40 km/h N/A (structural design)
Land Use Residential N/A
Page 4 of 39
,UNISA | Transportation Engineering Exam Answers
A.2 Design Hourly Volume for the Year 2036
Question: Given the 2026 ADT = 5000 veh/day per direction, k factor = 0.14, annual traffic
growth = 5%, directional distribution factor = 50%, determine the design hourly volume in
2036.
Step 1: Determine the ADT in 2036.
The traffic growth formula is:
ADT2036 = ADT2026 × (1 + r)n (1)
Where:
• ADT2026 = 5000 veh/day/direction
• r = 0.05 (5% annual growth rate)
• n = 2036 − 2026 = 10 years
Therefore:
ADT2036 = 5000 × (1 + 0.05)10 (2)
ADT2036 = 5000 × (1.05)10 (3)
(1.05)10 = 1.6289
ADT2036 = 5000 × 1.6289 = 8 144.5 ≈ 8 145 veh/day/direction (4)
Step 2: Apply the directional distribution factor.
The problem states the ADT is already given per direction (one direction), so the directional
factor of 50% is already accounted for in the 5000 veh/day/direction figure. Therefore the de-
sign ADT in 2036 per direction remains:
ADT2036,direction = 8 145 veh/day (5)
Step 3: Calculate the Design Hourly Volume (DHV).
Page 5 of 39
,UNISA | Transportation Engineering Exam Answers
The DHV is calculated using the k-factor:
DHV = ADT2036 × k (6)
DHV = 8 145 × 0.14 (7)
DHV = 1 140.3 ≈ 1 140 veh/hour (8)
Implementation Insight
The design hourly volume of approximately 1 140 veh/h in 2036 is used for geometric
design and intersection capacity analysis of the road in the target year.
Page 6 of 39
, UNISA | Transportation Engineering Exam Answers
A.3 Four-Lane Divided Highway Cross-Section
Given cross-sectional dimensions:
• Depressed median width: 9.0 m
• Lane width: 3.6 m
• Inner shoulder width: 0.8 m
• Outer shoulder width: 2.0 m
• Number of lanes: 4 (2 per direction)
A.3.1 River Basin Maps and Highway Location
Question: Briefly explain how river basin maps, obtained during desk study, are useful in
terms of the location of the highway.
River basin maps are topographic and hydrological maps that show drainage divides, water-
shed boundaries, stream networks, and flow directions. During the desk study phase of high-
way planning, these maps serve several important purposes:
1. Avoiding flood-prone areas: River basin maps identify low-lying valleys and flood-
plains where roads would be vulnerable to flooding. Highway alignments can be shifted
to higher ground to reduce this risk.
2. Identifying major water crossings: The maps show where streams and rivers cross
the proposed route corridor, enabling early planning for bridges or culverts and estimating
their approximate size.
3. Slope and terrain assessment: The drainage divide lines on river basin maps reveal
major ridgelines and valleys, helping the designer choose alignments that minimise steep
grades and excessive earthworks.
Implementation Insight
In central African countries, river basin maps are particularly valuable during desk
study because field surveys may be limited by access constraints. Early identification
of major drainage features can prevent costly re-alignment decisions later in the design
process.
Page 7 of 39
College of Science, Engineering and Technology
⋄ ⋄ ⋄ ⋄ ⋄ ⋄ ⋄ ⋄ ⋄⋄
TRANSPORTATION ENGINEERING,
PAVEMENT & GEOMETRIC DESIGN
Assignment 01 — 2026
⋄ ⋄ ⋄ ⋄ ⋄ ⋄ ⋄ ⋄ ⋄⋄
TPG3700
Module:
01
Assignment :
A, B, C, D, E, F, G, H, I, J
Questions Covered:
100
Total Marks:
2026
Year:
Transportation Engineering Examination — Detailed Solutions
,UNISA | Transportation Engineering Exam Answers
Contents
1 Question A: Road Classification and Design 4
1.1 A.1 TRH26 Classification of a U5b Road and TRH4 Equivalent . . . . . 4
1.2 A.2 Design Hourly Volume for the Year 2036 . . . . . . . . . . . . . . . . 5
1.3 A.3 Four-Lane Divided Highway Cross-Section . . . . . . . . . . . . . . . . 7
1.3.1 A.3.1 River Basin Maps and Highway Location . . . . . . . . . . . . . . . 7
1.3.2 A.3.2 Carriageway Width and Travelled Way Width . . . . . . . . . . . . 8
2 Question B: Traffic Signals 9
2.1 B.1 Traffic Signal Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.1.1 B.1.1 Signal Phase and Signal Cycle . . . . . . . . . . . . . . . . . . . . . 9
2.1.2 B.1.2 Pre-Timed and Demand-Actuated Traffic Signals . . . . . . . . . . . 9
2.2 B.2 Pre-Timed Intersection – Green Interval Calculation . . . . . . . . . 10
3 Question C: Stopping Sight Distance 14
3.1 C.1 Perception-Reaction Time . . . . . . . . . . . . . . . . . . . . . . . . . . 14
3.2 C.2 Brake Force Coefficient from TRH17 . . . . . . . . . . . . . . . . . . . 14
3.3 C.3 Minimum SSD on a Flat (Levelled) Road Section . . . . . . . . . . . 15
3.4 C.4 SSD on a Road Section with 5% Gradient . . . . . . . . . . . . . . . . 16
3.5 C.5 Comparison with TRH17 Recommended Values . . . . . . . . . . . . 16
4 Question D: Superelevation and Circular Curve Verification 18
5 Question E: Horizontal Curve Geometry 20
5.1 E.1 Curve Central Angle, Length, and Deflection Angle at 1+038.491 . 20
5.2 E.2 Total Widening Requirement for Articulated Bus . . . . . . . . . . . 21
5.3 E.3 Sight Distance Check for Building 15 m from Edge of Road . . . . . 22
Page 2 of 39
,UNISA | Transportation Engineering Exam Answers
6 Question F: Superelevation Transition 24
6.1 F.1 Transition Stations (Points of Change) . . . . . . . . . . . . . . . . . . 24
6.2 F.2 Length of Fully Superelevated Circular Curve . . . . . . . . . . . . . . 25
6.3 F.3 Superelevation Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
7 Question G: Vertical Alignment – Sag Curve 27
7.1 G.1 Chainages and Elevations of BVC, EVC, and Lowest Point . . . . . 27
7.2 G.2 Minimum Curve Length per TRH17 Rate of Vertical Curvature . . 29
7.3 G.3 Curve Length Safety Check for Minimum SSD = 149 m . . . . . . . 29
7.4 G.4 Drainage Requirements and Minimum Grade . . . . . . . . . . . . . . 30
8 Question H: Subgrade CBR Analysis and TRH4 Design 31
9 Question I: Equivalent E80 Calculations 34
9.1 I.1 Equivalent Daily E80s from Axle Load Count . . . . . . . . . . . . . . 34
9.2 I.2 Pavement Class (ES) for New 4-Lane Divided Road . . . . . . . . . . 36
10 Question J: TRH4 Pavement Structure Design 38
10.1 J.1 All Possible Alternative Pavement Structures from TRH4 . . . . . . 38
10.2 J.2 Neat Sketches of Alternative Pavement Structures . . . . . . . . . . . 39
Page 3 of 39
,UNISA | Transportation Engineering Exam Answers
Question A: Road Classification and Design
A.1 TRH26 Classification of a U5b Road and TRH4 Equivalent
Question: Use TRH26 guidelines to classify a U5b road. Also provide the closest equivalent
class given in TRH4.
TRH26 Classification of U5b:
Under the TRH26 framework, roads are classified by function, land use context, and traffic
volumes. A U5b road falls within the urban road hierarchy as follows:
• Category U: Urban road network
• Level 5: Local access road serving residential land uses at the lowest functional level
• Sub-class b: Low volume, primarily serving pedestrians and slow-moving vehicles, with
traffic volumes typically below 500 vehicles per day (vpd)
A U5b road is a minor local street or access road within a residential area. It has minimal
through-traffic, low posted speeds (generally 30–40 km/h), and its primary role is to provide
direct property access rather than to carry through-traffic.
Closest TRH4 Equivalent:
TRH4 classifies roads by category based on traffic loading (equivalent 80 kN single-axle loads,
E80s) and environmental conditions. The closest equivalent to a U5b road in TRH4 is:
Key Distinction
TRH4 Category: ES1 or ES2 (low-volume pavement category). U5b roads carry
very low traffic and therefore require only light pavement design, corresponding to the
lowest TRH4 traffic loading class.
Table 1: TRH26 vs TRH4 Road Class Comparison
Aspect TRH26 (U5b) TRH4 Equivalent
Function Local access Low-volume pavement
Volume Below 500 vpd ES1/ES2 class
Speed 30–40 km/h N/A (structural design)
Land Use Residential N/A
Page 4 of 39
,UNISA | Transportation Engineering Exam Answers
A.2 Design Hourly Volume for the Year 2036
Question: Given the 2026 ADT = 5000 veh/day per direction, k factor = 0.14, annual traffic
growth = 5%, directional distribution factor = 50%, determine the design hourly volume in
2036.
Step 1: Determine the ADT in 2036.
The traffic growth formula is:
ADT2036 = ADT2026 × (1 + r)n (1)
Where:
• ADT2026 = 5000 veh/day/direction
• r = 0.05 (5% annual growth rate)
• n = 2036 − 2026 = 10 years
Therefore:
ADT2036 = 5000 × (1 + 0.05)10 (2)
ADT2036 = 5000 × (1.05)10 (3)
(1.05)10 = 1.6289
ADT2036 = 5000 × 1.6289 = 8 144.5 ≈ 8 145 veh/day/direction (4)
Step 2: Apply the directional distribution factor.
The problem states the ADT is already given per direction (one direction), so the directional
factor of 50% is already accounted for in the 5000 veh/day/direction figure. Therefore the de-
sign ADT in 2036 per direction remains:
ADT2036,direction = 8 145 veh/day (5)
Step 3: Calculate the Design Hourly Volume (DHV).
Page 5 of 39
,UNISA | Transportation Engineering Exam Answers
The DHV is calculated using the k-factor:
DHV = ADT2036 × k (6)
DHV = 8 145 × 0.14 (7)
DHV = 1 140.3 ≈ 1 140 veh/hour (8)
Implementation Insight
The design hourly volume of approximately 1 140 veh/h in 2036 is used for geometric
design and intersection capacity analysis of the road in the target year.
Page 6 of 39
, UNISA | Transportation Engineering Exam Answers
A.3 Four-Lane Divided Highway Cross-Section
Given cross-sectional dimensions:
• Depressed median width: 9.0 m
• Lane width: 3.6 m
• Inner shoulder width: 0.8 m
• Outer shoulder width: 2.0 m
• Number of lanes: 4 (2 per direction)
A.3.1 River Basin Maps and Highway Location
Question: Briefly explain how river basin maps, obtained during desk study, are useful in
terms of the location of the highway.
River basin maps are topographic and hydrological maps that show drainage divides, water-
shed boundaries, stream networks, and flow directions. During the desk study phase of high-
way planning, these maps serve several important purposes:
1. Avoiding flood-prone areas: River basin maps identify low-lying valleys and flood-
plains where roads would be vulnerable to flooding. Highway alignments can be shifted
to higher ground to reduce this risk.
2. Identifying major water crossings: The maps show where streams and rivers cross
the proposed route corridor, enabling early planning for bridges or culverts and estimating
their approximate size.
3. Slope and terrain assessment: The drainage divide lines on river basin maps reveal
major ridgelines and valleys, helping the designer choose alignments that minimise steep
grades and excessive earthworks.
Implementation Insight
In central African countries, river basin maps are particularly valuable during desk
study because field surveys may be limited by access constraints. Early identification
of major drainage features can prevent costly re-alignment decisions later in the design
process.
Page 7 of 39
