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PDF (DX094490.pdf) - White Rose Etheses Online

PDF (DX094490.pdf) - White Rose Etheses Online

104 the study sites. The

104 the study sites. The headways produced by the simulation were then analysed to provide counting distributions for each of the separate values of T. These distributions were then used as theoretical distributions to compare them with the observed ones. This method would allow the determination of whether the best model to describe the real flows was the simple negative exponential or a shifted negative exponential; furthermore, it should be possible to arrive at a suitable value for the shift, T. For Castle Square, three values of T were used in the simulation, 0.00, 0.50 and 1.00 sec. When the observed counting distribution was compared, the hypothesis that it was the same as the simulated could not be rejected for the cases of T = 0.00 and T = 0.50 sec, while it was rejected for T = 1.00 sec. For Moore Street, the hypothesis was not rejected for T = 0.00 sec, only; both other cases were rejected. The simulated flows were then analysed to produce headway distributions using values of T varying from 0.0 to 1.0 sec in 0.1 sec increments. These were compared with the headway distribution obtained at Castle Square but the hypothesis that they were similar was rejected for all values of 'r. However the ones that caine nearest to the value that would have permitted no rejection were in the region of T = 0.60 - 0.75 sec, contrary to expectations. Inspecting the results it could be seen that the main contributors to the difference were the intervals 0 - 1.0 sec and 1.0 - 2.0 sec, the first two, which contain the smallest offered gaps. This 2 can be seen in Table 4.32 which shows the x -test for two theoretical exponential distributions and the observed. The agreement in all other intervals was reasonable.

105 From the point of view of which gaps influence the behaviour of the entry flow, it is obvious that the most important ones are the ones which would allow vehicles to join the circulating flow, i.e. the ones larger than the critical gap. Therefore, the precise distribution of the gaps less than 2 seconds in the two categories would riot influence at all the capacity and delay of the entering vehicles. What is of more importance is that the total number of gaps in these two categories combined is similar in both simulated and observed distributions. Therefore, it was decided to repeat the X-test by combining the first two intervals of the distrib- utions. The results were radically different from the previous analysis. The values of t for which the hypothesis was not rejected were in the range of 0.00 to 0.40 sec with the value of t = 0.20 sec giving the lowest x 2 value. As this value was also the mid-point of the range, it was decided to adopt = 0.20 sec as the value to be used in the roundabout 2 snulation model. (See Table 4.33 for the x values obtained at this stage of the analysis.)

The Archaeology of Medieval Europe - White Rose Research Online
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PDF (267549_VOL2.pdf) - White Rose Etheses Online
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