TRANSPORTATION ENGINEERING, PAVEMENT &
GEOMETRIC DESIGN
Road Design, Traffic Engineering and Pavement Design
⋄
TPG3700 ASSIGNMENT 01
Questions A Through J — Complete Worked Solutions
⋄
Subject: Transport & Highway Engineering
Topics Covered: Road Classification, Traffic Engineering,
Geometric Design, Pavement Design
Total Marks: 100
Questions: A, B, C, D, E, F, G, H, I, J
Guidelines: TRH4, TRH17, TRH26
Complete worked solutions with step-by-step calculations
Transport and Highway Engineering Examination
,Transportation Engineering, Pavement & Geometric Design Exam Solutions
Contents
1 Question A: Road Classification and Design Hourly Volume 3
1.1 A.1 — TRH26 Classification of a U5b Road and TRH4 Equivalent . . . 3
1.2 A.2 — Design Hourly Volume for Year 2036 . . . . . . . . . . . . . . . . . 3
1.3 A.3 — 4-Lane Divided Highway Cross-Section . . . . . . . . . . . . . . . . 5
1.3.1 A.3.1 — River Basin Maps and Highway Location . . . . . . . . . . . . . 5
1.3.2 A.3.2 — Carriageway and Travelled Way Widths . . . . . . . . . . . . . . 5
2 Question B: Traffic Signals 7
2.1 B.1 — Signal Phase, Signal Cycle, Pre-timed and Demand-Actuated Sig-
nals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.1.1 B.1.1 — Signal Phase and Signal Cycle . . . . . . . . . . . . . . . . . . . . 7
2.1.2 B.1.2 — Pre-timed and Demand-Actuated Traffic Signals . . . . . . . . . 7
2.2 B.2 — Pre-timed Intersection: Green Interval Calculation . . . . . . . . 7
3 Question C: Stopping Sight Distance 12
3.1 C.1 — Perception-Reaction Time . . . . . . . . . . . . . . . . . . . . . . . . 12
3.2 C.2 — Brake Force Coefficient from TRH17 . . . . . . . . . . . . . . . . . 12
3.3 C.3 — Minimum SSD on a Flat Road Section . . . . . . . . . . . . . . . . 13
3.4 C.4 — SSD on a Road Section with 5% Gradient . . . . . . . . . . . . . . 14
3.5 C.5 — Comparison with TRH17 Recommended Values . . . . . . . . . . 14
4 Question D: Circular Curve Superelevation Verification 16
5 Question E: Horizontal Curve Geometry 18
5.1 E.1 — Curve Central Angle, Length, and Deflection Angle at 1+038.491 18
5.2 E.2 — Total Widening Requirement for Articulated Bus . . . . . . . . . 19
Page 1 of 37
,Transportation Engineering, Pavement & Geometric Design Exam Solutions
5.3 E.3 — Building Safety Check (15 m from Edge of Road) . . . . . . . . . 20
6 Question F: Superelevation Development on Transition Curves 22
6.1 F.1 — Transition Stations at Points of Change . . . . . . . . . . . . . . . . 22
6.2 F.2 — Length of Circular Curve that is Fully Superelevated . . . . . . . 24
6.3 F.3 — Superelevation Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . 24
7 Question G: Vertical Curve (Sag Curve) 26
7.1 G.1 — Chainages and Elevations of BVC, EVC, and Lowest Point . . . 26
7.2 G.2 — Minimum Curve Length Check (Rate of Vertical Curvature) . . 27
7.3 G.3 — Verification for Minimum SSD = 149 m . . . . . . . . . . . . . . . 28
7.4 G.4 — Drainage Requirements and Minimum Grade . . . . . . . . . . . . 28
8 Question H: Subgrade CBR and TRH4 Design 30
9 Question I: Pavement Design – E80 Calculations 32
9.1 I.1 — Equivalent Daily E80s . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
9.2 I.2 — Pavement Class (ES) for New 4-Lane Road . . . . . . . . . . . . . . 33
10 Question J: Alternative Pavement Structures (TRH4) 35
10.1 J.1 — Alternative Pavement Structures from TRH4 Table 19 . . . . . . 35
10.2 J.2 — Neat Sketches of Alternative Pavement Structures . . . . . . . . . 36
Page 2 of 37
,Transportation Engineering, Pavement & Geometric Design Exam Solutions
Question A: Road Classification and Design Hourly Volume
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 the TRH4.
Answer:
Under TRH26, the classification system for urban roads uses a combination of a letter prefix
and a numerical-letter suffix to describe function and volume. For a U5b road:
• U denotes an urban road.
• 5 refers to the road category, which in TRH26 corresponds to a local distributor or ac-
cess road, carrying relatively low traffic volumes and providing access to properties and
local areas.
• b indicates the lower sub-category within category 5, meaning this road has lower traffic
volumes compared to a U5a road.
A U5b road functions as a local access street with limited through-traffic. It connects neigh-
bourhoods to higher-order roads and serves direct land access.
Key Distinction
TRH4 Equivalent: The closest TRH4 equivalent to a U5b (TRH26) road is Class
5 (also written as Category 5), which corresponds to a local road or minor collector.
TRH4 classifies roads by function from Class 1 (primary distributors, major national
routes) down to Class 5 (local access roads and minor streets). A U5b, being a low-
volume urban access road, maps directly onto TRH4 Class 5.
A.2 — Design Hourly Volume for Year 2036
Question: Given the 2026 ADT = 5000 veh/day per direction of travel, k factor = 0.14,
annual traffic growth is 5%, and directional distribution factor is 50%, determine the design
hourly volume in the year 2036.
Answer:
Step 1: Determine the future ADT in 2036.
Page 3 of 37
,Transportation Engineering, Pavement & Geometric Design Exam Solutions
The number of years of growth from 2026 to 2036 is:
n = 2036 − 2026 = 10 years
The growth rate is i = 5% = 0.05 per year. The future ADT is calculated as:
ADT2036 = ADT2026 × (1 + i)n
ADT2036 = 5000 × (1 + 0.05)10
ADT2036 = 5000 × (1.05)10
(1.05)10 = 1.6289
ADT2036 = 5000 × 1.6289 = 8144.5 ≈ 8145 veh/day per direction
Step 2: Apply the k factor to find the Design Hourly Volume (DHV).
The k factor converts daily volume to the design (30th highest) hourly volume:
DHV = ADT2036 × k
DHV = 8145 × 0.14 = 1140.3 ≈ 1140 veh/h (total, both directions)
Step 3: Apply the directional distribution factor.
The directional distribution factor D = 50% = 0.50, meaning traffic splits equally in both
directions. Therefore:
DDHV = DHV × D = 1140 × 0.50 = 570 veh/h per direction
Implementation Insight
The Design Directional Hourly Volume (DDHV) in 2036 is 570 vehicles per hour
in the design direction. This value is used for capacity analysis and lane design of the
road.
Page 4 of 37
,Transportation Engineering, Pavement & Geometric Design Exam Solutions
A.3 — 4-Lane Divided Highway Cross-Section
Given: Depressed median = 9.0 m, lane width = 3.6 m, inner shoulder width = 0.8 m, outer
shoulder width = 2.0 m.
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.
Answer:
River basin maps show the drainage network, watershed boundaries, and topographic flow
patterns of a region. During the desk study phase of road planning, these maps help the high-
way engineer in the following ways:
1. Avoiding flood-prone areas: River basins indicate valleys and low-lying areas that
flood seasonally. Routing the highway through these zones increases construction cost and
flood risk.
2. Identifying major crossings: The maps reveal where the road alignment must cross
rivers or streams, which drives bridge and culvert design requirements.
3. Natural drainage direction: Understanding basin divides allows the road alignment to
follow ridge lines where feasible, reducing the number of drainage structures required.
4. Minimising environmental impact: Sensitive riparian zones are visible on river basin
maps; the engineer can route around them to comply with environmental regulations.
5. Earthworks planning: Ridgeline routing (identifiable from basin maps) tends to reduce
cut and fill volumes compared to valley routing.
A.3.2 — Carriageway and Travelled Way Widths
Question: Calculate the widths of the carriageway and travelled way.
Answer:
The road is a 4-lane divided highway, meaning there are 2 lanes in each direction (2 lanes per
carriageway). Each carriageway is separated by the depressed median.
Step 1: Calculate the Travelled Way width per carriageway.
Page 5 of 37
, Transportation Engineering, Pavement & Geometric Design Exam Solutions
The travelled way includes only the traffic lanes:
Travelled Way = Number of lanes per carriageway × lane width
Travelled Way = 2 × 3.6 = 7.2 m per carriageway
Step 2: Calculate the Carriageway width per carriageway.
The carriageway includes the traffic lanes plus both shoulders:
Carriageway width = Inner shoulder + Travelled way + Outer shoulder
Carriageway width = 0.8 + 7.2 + 2.0 = 10.0 m per carriageway
Step 3: Total formation width (for reference).
The total road formation width for both carriageways and the median is:
Total width = Carriageway (left) + Median + Carriageway (right)
Total width = 10.0 + 9.0 + 10.0 = 29.0 m
Table 1: Summary of Cross-Section Widths
Component Width (m)
Inner shoulder (each side) 0.8
Lane width (each lane) 3.6
Outer shoulder (each side) 2.0
Travelled Way (per car- 7.2
riageway)
Carriageway (per side) 10.0
Depressed median 9.0
Total formation width 29.0
Page 6 of 37
GEOMETRIC DESIGN
Road Design, Traffic Engineering and Pavement Design
⋄
TPG3700 ASSIGNMENT 01
Questions A Through J — Complete Worked Solutions
⋄
Subject: Transport & Highway Engineering
Topics Covered: Road Classification, Traffic Engineering,
Geometric Design, Pavement Design
Total Marks: 100
Questions: A, B, C, D, E, F, G, H, I, J
Guidelines: TRH4, TRH17, TRH26
Complete worked solutions with step-by-step calculations
Transport and Highway Engineering Examination
,Transportation Engineering, Pavement & Geometric Design Exam Solutions
Contents
1 Question A: Road Classification and Design Hourly Volume 3
1.1 A.1 — TRH26 Classification of a U5b Road and TRH4 Equivalent . . . 3
1.2 A.2 — Design Hourly Volume for Year 2036 . . . . . . . . . . . . . . . . . 3
1.3 A.3 — 4-Lane Divided Highway Cross-Section . . . . . . . . . . . . . . . . 5
1.3.1 A.3.1 — River Basin Maps and Highway Location . . . . . . . . . . . . . 5
1.3.2 A.3.2 — Carriageway and Travelled Way Widths . . . . . . . . . . . . . . 5
2 Question B: Traffic Signals 7
2.1 B.1 — Signal Phase, Signal Cycle, Pre-timed and Demand-Actuated Sig-
nals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.1.1 B.1.1 — Signal Phase and Signal Cycle . . . . . . . . . . . . . . . . . . . . 7
2.1.2 B.1.2 — Pre-timed and Demand-Actuated Traffic Signals . . . . . . . . . 7
2.2 B.2 — Pre-timed Intersection: Green Interval Calculation . . . . . . . . 7
3 Question C: Stopping Sight Distance 12
3.1 C.1 — Perception-Reaction Time . . . . . . . . . . . . . . . . . . . . . . . . 12
3.2 C.2 — Brake Force Coefficient from TRH17 . . . . . . . . . . . . . . . . . 12
3.3 C.3 — Minimum SSD on a Flat Road Section . . . . . . . . . . . . . . . . 13
3.4 C.4 — SSD on a Road Section with 5% Gradient . . . . . . . . . . . . . . 14
3.5 C.5 — Comparison with TRH17 Recommended Values . . . . . . . . . . 14
4 Question D: Circular Curve Superelevation Verification 16
5 Question E: Horizontal Curve Geometry 18
5.1 E.1 — Curve Central Angle, Length, and Deflection Angle at 1+038.491 18
5.2 E.2 — Total Widening Requirement for Articulated Bus . . . . . . . . . 19
Page 1 of 37
,Transportation Engineering, Pavement & Geometric Design Exam Solutions
5.3 E.3 — Building Safety Check (15 m from Edge of Road) . . . . . . . . . 20
6 Question F: Superelevation Development on Transition Curves 22
6.1 F.1 — Transition Stations at Points of Change . . . . . . . . . . . . . . . . 22
6.2 F.2 — Length of Circular Curve that is Fully Superelevated . . . . . . . 24
6.3 F.3 — Superelevation Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . 24
7 Question G: Vertical Curve (Sag Curve) 26
7.1 G.1 — Chainages and Elevations of BVC, EVC, and Lowest Point . . . 26
7.2 G.2 — Minimum Curve Length Check (Rate of Vertical Curvature) . . 27
7.3 G.3 — Verification for Minimum SSD = 149 m . . . . . . . . . . . . . . . 28
7.4 G.4 — Drainage Requirements and Minimum Grade . . . . . . . . . . . . 28
8 Question H: Subgrade CBR and TRH4 Design 30
9 Question I: Pavement Design – E80 Calculations 32
9.1 I.1 — Equivalent Daily E80s . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
9.2 I.2 — Pavement Class (ES) for New 4-Lane Road . . . . . . . . . . . . . . 33
10 Question J: Alternative Pavement Structures (TRH4) 35
10.1 J.1 — Alternative Pavement Structures from TRH4 Table 19 . . . . . . 35
10.2 J.2 — Neat Sketches of Alternative Pavement Structures . . . . . . . . . 36
Page 2 of 37
,Transportation Engineering, Pavement & Geometric Design Exam Solutions
Question A: Road Classification and Design Hourly Volume
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 the TRH4.
Answer:
Under TRH26, the classification system for urban roads uses a combination of a letter prefix
and a numerical-letter suffix to describe function and volume. For a U5b road:
• U denotes an urban road.
• 5 refers to the road category, which in TRH26 corresponds to a local distributor or ac-
cess road, carrying relatively low traffic volumes and providing access to properties and
local areas.
• b indicates the lower sub-category within category 5, meaning this road has lower traffic
volumes compared to a U5a road.
A U5b road functions as a local access street with limited through-traffic. It connects neigh-
bourhoods to higher-order roads and serves direct land access.
Key Distinction
TRH4 Equivalent: The closest TRH4 equivalent to a U5b (TRH26) road is Class
5 (also written as Category 5), which corresponds to a local road or minor collector.
TRH4 classifies roads by function from Class 1 (primary distributors, major national
routes) down to Class 5 (local access roads and minor streets). A U5b, being a low-
volume urban access road, maps directly onto TRH4 Class 5.
A.2 — Design Hourly Volume for Year 2036
Question: Given the 2026 ADT = 5000 veh/day per direction of travel, k factor = 0.14,
annual traffic growth is 5%, and directional distribution factor is 50%, determine the design
hourly volume in the year 2036.
Answer:
Step 1: Determine the future ADT in 2036.
Page 3 of 37
,Transportation Engineering, Pavement & Geometric Design Exam Solutions
The number of years of growth from 2026 to 2036 is:
n = 2036 − 2026 = 10 years
The growth rate is i = 5% = 0.05 per year. The future ADT is calculated as:
ADT2036 = ADT2026 × (1 + i)n
ADT2036 = 5000 × (1 + 0.05)10
ADT2036 = 5000 × (1.05)10
(1.05)10 = 1.6289
ADT2036 = 5000 × 1.6289 = 8144.5 ≈ 8145 veh/day per direction
Step 2: Apply the k factor to find the Design Hourly Volume (DHV).
The k factor converts daily volume to the design (30th highest) hourly volume:
DHV = ADT2036 × k
DHV = 8145 × 0.14 = 1140.3 ≈ 1140 veh/h (total, both directions)
Step 3: Apply the directional distribution factor.
The directional distribution factor D = 50% = 0.50, meaning traffic splits equally in both
directions. Therefore:
DDHV = DHV × D = 1140 × 0.50 = 570 veh/h per direction
Implementation Insight
The Design Directional Hourly Volume (DDHV) in 2036 is 570 vehicles per hour
in the design direction. This value is used for capacity analysis and lane design of the
road.
Page 4 of 37
,Transportation Engineering, Pavement & Geometric Design Exam Solutions
A.3 — 4-Lane Divided Highway Cross-Section
Given: Depressed median = 9.0 m, lane width = 3.6 m, inner shoulder width = 0.8 m, outer
shoulder width = 2.0 m.
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.
Answer:
River basin maps show the drainage network, watershed boundaries, and topographic flow
patterns of a region. During the desk study phase of road planning, these maps help the high-
way engineer in the following ways:
1. Avoiding flood-prone areas: River basins indicate valleys and low-lying areas that
flood seasonally. Routing the highway through these zones increases construction cost and
flood risk.
2. Identifying major crossings: The maps reveal where the road alignment must cross
rivers or streams, which drives bridge and culvert design requirements.
3. Natural drainage direction: Understanding basin divides allows the road alignment to
follow ridge lines where feasible, reducing the number of drainage structures required.
4. Minimising environmental impact: Sensitive riparian zones are visible on river basin
maps; the engineer can route around them to comply with environmental regulations.
5. Earthworks planning: Ridgeline routing (identifiable from basin maps) tends to reduce
cut and fill volumes compared to valley routing.
A.3.2 — Carriageway and Travelled Way Widths
Question: Calculate the widths of the carriageway and travelled way.
Answer:
The road is a 4-lane divided highway, meaning there are 2 lanes in each direction (2 lanes per
carriageway). Each carriageway is separated by the depressed median.
Step 1: Calculate the Travelled Way width per carriageway.
Page 5 of 37
, Transportation Engineering, Pavement & Geometric Design Exam Solutions
The travelled way includes only the traffic lanes:
Travelled Way = Number of lanes per carriageway × lane width
Travelled Way = 2 × 3.6 = 7.2 m per carriageway
Step 2: Calculate the Carriageway width per carriageway.
The carriageway includes the traffic lanes plus both shoulders:
Carriageway width = Inner shoulder + Travelled way + Outer shoulder
Carriageway width = 0.8 + 7.2 + 2.0 = 10.0 m per carriageway
Step 3: Total formation width (for reference).
The total road formation width for both carriageways and the median is:
Total width = Carriageway (left) + Median + Carriageway (right)
Total width = 10.0 + 9.0 + 10.0 = 29.0 m
Table 1: Summary of Cross-Section Widths
Component Width (m)
Inner shoulder (each side) 0.8
Lane width (each lane) 3.6
Outer shoulder (each side) 2.0
Travelled Way (per car- 7.2
riageway)
Carriageway (per side) 10.0
Depressed median 9.0
Total formation width 29.0
Page 6 of 37
