Next Generation Simulation (NGSIM)
-Improved Simulation of Stop Bar Driver Behavior at Signalized Intersections-
Los Angeles, CA and Atlanta, GA Data Sets

Working Papers

The results of a series of experiments carried out to determine the starting characteristics of automobile platoons are reported. In particular, the space-time trajectories of the lead and last vehicles have been examined in greater detail in order to determine the macroscopic properties of vehicular platoons. The effect of such factors such as initial intervehicle spacing, speed, starting delay and acceleration behavior are presented. In addition, calculations have been made for the flow of the platoon as a function of position along the roadway as well as for the speed of propagation of the starting wave as the platoon accelerates up to speed.

This article appeared in Traffic Flow and Transportation, Proceedings of the Fifth International Symposium on the Theory of Traffic Flow and Transportation.

Summary

This paper presents the results of a study about starting dynamics of a queue composed of similar automobiles on a test track facility. A platoon of 6 vehicles was used; all of them were of the same model except the first one which held all the measuring equipment. The entire experiment basically consisted of giving the lead vehicle driver specific instructions about acceleration, etc. while telling the rest of the platoon to follow the leading car in a ‘normal and safe’ manner. A single lane was used on the straight part of the two-lane track facility for all the test runs. The lead car was told to drive at three different acceleration rates, low, medium and high (4, 8 and 12ft/s²), and the vehicle characteristics (speed, acceleration and position) of the first and the last cars were noted.

Some significant observations include:

• (Mean) Acceleration has inverse linear relationship with speed. For higher initial acceleration rates, acceleration-speed curves are steeper and vice versa.
• For low and medium lead car acceleration runs, platoon length had a direct relationship with speed of last car at the moment of time it started its first acceleration correction.
• Speed of propagation of the starting wave varied directly with the platoon speed, and also with the acceleration.
• Drivers of automobiles (which themselves vary widely in performance) make a number of corrections as they accelerate up to speed, as opposed to bus platoon drivers which typically make only one correction.
• Speed of propagation of any disturbance is a constant determined by the initial platoon length and the starting delay.