What distinguishes Time Mean Speed (TMS) from Space Mean Speed (SMS)?

Time Mean Speed (TMS) is distinguished from Space Mean Speed (SMS) primarily based on the methodology used for calculating average speed in relation to either time or distance. TMS reflects the average speed of all vehicles passing a specific point over a defined time period, which means it emphasizes the speed behavior of vehicles as they arrive at that point. This measure is particularly useful for understanding traffic conditions as experienced by drivers at a specific location throughout a certain interval.

Conversely, SMS provides an average speed that is representative of a given segment of roadway and is calculated by considering the distance traveled and time taken by vehicles within that section. Unlike TMS, which is point-based, SMS is concerned with the entire length of the roadway segment and how long it takes vehicles to traverse that distance. Hence, it accounts for the varying speeds of vehicles along the length of the roadway, which is crucial for understanding overall traffic flow and the efficiency of the roadway segment.

Option B captures this distinction accurately by stating that TMS involves the average speed of vehicles over a time period, while SMS pertains to vehicles traveling on a particular roadway section, directly reflecting how each measure is utilized to assess traffic dynamics differently.