Traffic Engineering MCQ Quiz - Objective Question with Answer for Traffic Engineering - Download Free PDF

Explanation:

• IRC 37 states that rotary (or roundabout) intersections can handle up to around 3000 vehicles per hour entering from all approaches efficiently.

• When entering traffic exceeds this volume, the rotary may experience congestion, increasing delays and reducing safety.

• For traffic volumes higher than 3000 vehicles per hour, other intersection designs like signalized intersections or flyovers are preferred.

• Proper design and size of the rotary are important to maintain smooth traffic flow at these volumes.

 Additional Information

Rotary (or roundabout) is a circular intersection where traffic moves around a central island in one direction. It controls traffic flow without the need for signals or stop signs.

• Vehicles entering the rotary give way to traffic already circulating, improving continuous flow and reducing delays.

• Rotaries reduce conflict points compared to traditional intersections, lowering the risk of severe accidents.

• They are suitable for moderate traffic volumes and help in traffic calming by slowing vehicle speeds.

• Proper design of entry angles, circulating lane width, and signage is essential for safety and efficiency.

• Rotaries can handle different traffic volumes but have a maximum capacity beyond which other intersection types are better.

Explanation:

• This study helps in assessing:

  • Traffic congestion patterns

  • Delays due to intersections, signals, or bottlenecks

  • Travel speeds under prevailing conditions

• The ultimate goal is to evaluate the efficiency and quality of movement, not merely the raw time data.

• It is a key tool in traffic management and urban mobility planning.

Explanation: 

• Yellow markings are not exclusively regulatory. They are primarily used to separate traffic flows in opposite directions and indicate no-overtaking zones, centerlines, etc.

• White markings are used for lane separation (same direction), edge lines, guidance, and also regulatory purposes (like stop lines, turn arrows).

Additional Information

Purpose of Traffic Markings

Traffic markings are used on roads to:

• Regulate traffic flow

• Ensure safety

• Guide and warn drivers

• Indicate road conditions and lane usage

Classification of Road Markings

Longitudinal Markings

• Run parallel to the direction of traffic.

• Examples: lane lines, centerlines, edge lines.

• Help in lane discipline, no-overtaking zones, and direction control.

Transverse Markings

• Run across the roadway.

• Examples: stop lines, pedestrian crossings, give way (yield) lines.

• Used to control movement at intersections and crossings.

Hazard/Object Markings

• Indicate presence of obstacles such as medians, bridge piers, or narrowings.

• Painted diagonally or chevron-style to draw attention.

Arrow Markings & Symbols

• Show specific instructions like turn directions, lane usage, etc.

Color Coding

• White Lines: Separate lanes in the same direction, mark edges, guide vehicles.

• Yellow Lines: Separate opposing traffic, indicate no-passing zones or medians.

• Red/Black: Used sparingly, often in special contexts (e.g., bus lanes or emergency zones).

• Other Colors (like Blue): Can indicate reserved parking, disabled zones, etc.

Explanation:

Full Cloverleaf Interchange (Correct Answer)

• Provides complete grade separation and free-flow for all turning movements.

• Characterized by four loop ramps in a cloverleaf shape.

• Suitable for high-speed traffic with no signal control.

• Eliminates need for left-turning vehicles to cross opposing traffic.

• Requires large land area.

Additional InformationRotary intersection

• A type of at-grade intersection (not grade-separated).

• Vehicles enter a central circular island and exit at desired roads.

• Traffic flows in one direction around the central island.

• Suitable for moderate traffic volumes at junctions of 3+ roads.

• Not used for high-speed highways.

Partial Cloverleaf Interchange

• Also called a parclo.

• Provides some but not all loops of a full cloverleaf.

• Used when land is limited or turning volumes are not high.

• Cheaper and requires less space than full cloverleaf.

• May involve some signalized turns depending on design.

Diamond Interchange

• Used where a major road crosses a minor road.

• Has four ramps forming a diamond shape.

• Turns onto/off the highway are usually signal- or stop-controlled at intersections.

• More compact and economical than cloverleaf.

• Common near urban areas and expressway exits.

Explanation:

Classification of traffic signs:

1) Mandatory/Regulatory sign:

• The regulatory or mandatory signs are used to inform the road Users of certain laws and regulations to provide safety and free flow to traffic.
• Shape: Circular

​Note:

Exception: Stop and Give way sign

The stop sign is octagonal in shape and the Give Way sign has the shape of an inverted triangle.

2) Warning sign:

• These signs are used to warn the road users at sufficient distance in advance about the impending road condition.
• Warning signs are also known as cautionary signs.
• Shape: Triangle

3) Informatory sign:

• Informatory signs are provided to guide the road user about the routes, destination, and to provide information that makes travel easier, safe, and pleasant.
• Shape: Rectangle

Concept:

Theoretical maximum capacity is given by,

\(C = \frac{{1000\;V}}{S}\)

Where,

C = is capacity is vehicle/hr

V = speed in km/hr

S = minimum clear distance between two vehicles

∴ S = 0.2 V + 6 ( if V is in kmph ) 

(or) S = 0.7 v + 6 ( if v is in m/s )

Calculation:

Given,

Velocity (V) = 40 kmph

∵ S = 0.2 V + 6 = 0.2 × 40 + 6 = 14 m

Theoretical Maximum capacity is given by,

\(C = \frac{{1000\;V}}{S}\)

\(C = \frac{{1000\; \times \ 40}}{14}\)

C = 2857.142 Veh/hr ≈ 2860 veh/hr

 Mandatory Sign (Regulatory sign) → Ex:- Give way, no entry, Stop, No parking

Cautionary sign(warning sign) → Ex:- Narrow road, narrow bridge.

Informatory sign → Ex:- Parking, bus stop

Concept:

Peak Hour Factor (PHF):

It compares the traffic volume during the busiest 15 minutes of the peak hour with the total volume during the peak hour. It indicates how consistent traffic volume is during the peak hour.

\(Peak\space Hour\space Factor(PHF)= {Total\space hourly \space volume \over Peak\space 15\space minute\space volume\space within\space the\space hour \times 4}\)

The Highway Capacity Manual advises that in absence of field measurements reasonable approximations for peak hour factor can be made as follows:

• 0.95 for congested condition
• 0.92 for urban areas
• 0.88 for rural areas 

Hence, The ‘Peak hour factor’ is defined as the ratio between the number of vehicles counted during the peak hour and four times the number counted during the highest fifteen consecutive minutes.

Explanation:

Number of possible conflict points for 3-legged intersections with 2 lanes and 2-way traffic = 9 

Number of possible conflict points for 4 legged intersections with 2 lanes and 2-way traffic = 24

Explanation:

Classification of signal:

1) Mandatory/Regulatory sign:

• The regulatory or mandatory signs are used to inform the road Users of certain laws and regulations to provide safety and free flow to traffic.
• Shape: Circular

Exception: Stop and Give way sign

The stop sign is octagonal in shape and the Give Way sign has the shape of an inverted triangle.

2) Warning sign:

• These signs are used to warn the road users at sufficient distance in advance about the impending road condition.
• Warning signs are also known as cautionary signs.
• Shape: Triangle

3) Informatory sign:

• Informatory signs are provided to guide the road user about the routes, destination, and to provide information that makes travel easier, safe, and pleasant.
• Shape: Rectangle

Concept:

Theoretical maximum capacity:

The maximum volume that can be possible on the road in the most ideal condition is called theoretical maximum capacity. It occurs with no jam, no congestion, and no delay condition.  It can be denoted by C. 

Theoretical maximum capacity, \({\bf{C}} = \frac{{1000{\bf\ {v}}}}{{\bf{S}}}\)

Where, v = Traffic flow speed(km/h)

S = Center to center spacing of vehicles(m)

C = Theoretical maximum capacity(vehicle/hour/lane)

Calculation:

Given, v = 40 km/h and S = 12.8 m

Theoretical maximum capacity, \({\bf{C}} = \frac{{1000{\bf\ {v}}}}{{\bf{S}}}\)

\({\bf{C}} = \frac{{1000 \times 40}}{{12.8}}\)

C = 3125 vehicle/hour/lane

Explanation:

Classification of sign in the road traffic:

1) Mandatory/Prohibitory sign:

• The regulatory or mandatory signs are used to inform the road Users of certain laws and regulations to provide safety and free flow to traffic.

2) Warning sign:

• These signs are used to warn the road users at sufficient distance in advance about the impending road condition.
• Warning signs are also known as cautionary signs.

3) Informatory sign:

• Informatory signs are provided to guide the road user about the routes, destination, and to provide information that makes travel easier, safe, and pleasant.