  This paper discusses the real-time prediction of queue lengths from probe
vehicles for the Bunch arrival headways at an isolated intersection for
undersaturated conditions. The paper incorporates the bunching effect of the
traffic into the evaluation of the accuracy of the predictions as a function of
proportion of probe vehicles to entire vehicle population. Formulations are
presented for predicting the expected queue length and its variance based on
Negative Exponential and Bunched Exponential vehicle headways. Numerical
results for both vehicle headway types are documented to show how prediction
errors behave by the volume to capacity ratio and probe proportions. It is
found that the Poisson arrivals generate conservative confidence intervals and
demand higher probe proportions compared to Bunched Exponential headways at the
same arrival rate and probe proportion.
