This paper studies some of the theoretical questions of large openings or gaps in a single stream of traffic. A gap in the traffic stream is defined as a headway between vehicles greater than or equal to some minimum size --say x. Several authors have studied the probability distribution of the wait which a randomly located observer must endure before he finds a gap. This paper, while briefly reviewing the solutions of this well known problem, is primarily concerned with expressions for: (i) the distribution of gap sizes; (ii) the distribution of spacings between vehicles and gaps; (iii) the mean and variance of inter-vehicle and intergap spacings; (iv) the stationary flow rates of gaps; and (v) the distribution of blocked and unblocked periods. It is assumed that the origin of measurements may be located (i) with the passing of a vehicle, (ii) at the beginning of a gap. or (iii) at random. It is also assumed that the distribution of inter-vehicle spacings are independently, but identically, distributed random variables.

■« A traffic counting distribution is derived in which a minimum spacing or headway between units of traffic is taken into account. A comparison is made between this probability distribution and the Type I Counter distribution derived by W. Feller (3). Explicit expressions are derived for the mean and variance of count as well as the probability that the interval of interest is completely filled by vehicles.