30.3.3. Journey speed

Journey speed is the effective speed of the vehicle on a journey between two points and is the distance between the two points divided by the total time taken for the vehicle to complete the journey including any stopped time.

Journey speed measures how fast a vehicle travels over a complete trip, from the starting point to the destination. To calculate it, we take the total distance covered and divide it by the total time taken for the journey, which includes any stops. This means that journey speed reflects the actual conditions of travel which may include times when the vehicle is stopped or moving slowly.

Think of journey speed like a trip you take in your car. If you are driving from your home to the grocery store, and you stop at traffic lights and take a while to find parking, your journey speed will be lower than if you cruised straight there without stopping. It's like measuring both the distance you traveled and how long it took, including any delays.

If the journey speed is less than running speed, it indicates that the journey follows a stop-go condition with enforced acceleration and deceleration.

When the journey speed is lower than the running speed, it suggests that the vehicle experiences frequent stops and starts. This could be due to traffic congestion, road conditions, or traffic signals requiring the driver to accelerate and then brake repeatedly. Such conditions can lead to less efficient travel, as it takes more time to complete the journey than simply maintaining a steady speed.

Imagine you're driving in a busy city filled with red lights and heavy traffic. You accelerate from a stop every time the light turns green, but you frequently have to stop again. Your car's speedometer might show a higher speed when you accelerate, but your overall journey takes much longer because of all the stopping and starting. This scenario illustrates how journey speed can be affected by stop-go conditions.

The spot speed here may vary from zero to some maximum in excess of the running speed. A uniformity between journey and running speeds denotes comfortable travel conditions.

In a typical journey, the individual speed at different points (referred to as spot speed) may show a wide range - for example, sometimes the vehicle might be stationary in a traffic jam, while at other times it might speed up to overtake slower vehicles. If journey speed aligns closely with running speed, it suggests that the journey is smooth and without many interruptions, indicating a more pleasant driving experience.

Consider a bicycle ride through a park. If you can pedal continuously without stopping too much (like when there's just a gentle slope and few people in your way), your journey speed matches your running speed. However, if you have to frequently dismount or slow down because of pedestrians, and then speed up again, your journey speed will be much lower than your potential speed when cycling on an empty path.

--