Question

The enoscope is used to determine

• A. travel time
• B. running speed
• C. spot speed
• D. average speed

Hint:

An enoscope is a basic tool for direct spot speed measurements, particularly useful in conditions where electronic equipment is unavailable or impractical. Other methods for spot speed include radar guns, speed traps, and video analysis.

Answer 1

The Correct Option is C

Step 1: Understand the purpose of traffic studies in highway engineering.
Traffic studies are conducted to collect data on traffic flow characteristics, which are essential for highway design, planning, and management. One important characteristic is speed. Different types of speed (spot speed, running speed, travel time, average speed) provide different insights into traffic behavior.
Step 2: Define "enoscope" and its application.
An enoscope is a simple device used in traffic engineering to measure spot speed. It consists of a box with a mirror inside, positioned at a specific angle (typically 45 degrees) to reflect vehicles from a detection zone to an observer. Observers typically set up two enoscopes at a known distance apart (e.g., 50m, 100m) along a road section. When a vehicle passes the first enoscope, the observer starts a stopwatch, and when it passes the second enoscope, the stopwatch is stopped.
Step 3: Distinguish between different types of speed measurements.

• Travel time: The total time taken to travel a specific length of a road, including all delays. It's usually measured over a longer route, not a short segment.
• Running speed: The speed of a vehicle when it is in motion. It's calculated by dividing the distance traveled by the actual time the vehicle is moving (excluding stops). This usually requires more detailed observation than a simple start/stop over a short segment.
• Spot speed: The instantaneous speed of a vehicle at a specific point or short section of a road. The enoscope method (along with radar guns, pressure plates, etc.) is designed to measure how fast a vehicle is moving at a particular location. By measuring the time taken to traverse a short, known distance between two enoscopes, the speed of the vehicle as it passes that 'spot' can be calculated.
• Average speed: Can refer to space mean speed or time mean speed. Space mean speed is the average speed of vehicles over a given section of road. Time mean speed is the average of spot speeds observed at a point over a period. While an enoscope study can contribute to calculating average spot speeds over time, its direct measurement is of individual vehicle's speed over a very short segment, which is "spot speed".

Step 4: Conclude the primary measurement of an enoscope.
The enoscope method is specifically designed to measure the speed of individual vehicles as they pass over a very short, predetermined length of road. This is the definition of spot speed. $$\boxed{\text{spot speed}}$$