00935368

Component

https://doi.org/10.3141/1804-01

http://scholar.google.com...Chen&publication_year=2002

Three methods for identifying outlying journey time observations collected as part of a motorway license plate matching exercise are presented. Each method is examined to ensure that it is comprehensible to transport practitioners, is able to correctly classify outliers, and is efficient in its application. The first method is a crude method based on percentiles. The second uses a mean absolute deviation test. The third method is a modification of a traditional z- or t-statistical test. Results from each method and combinations of methods are compared. The preferred method is judged to be the third method alone, which uses the median rather than the mean as its measure of location and the interquartile range rather than the standard deviation as its measure of variability. This method is seen to be robust to both the outliers themselves and the presence of incident conditions. The effectiveness of the method is demonstrated under a number of typical and atypical road traffic conditions. In particular, the method is applied to a different section of motorway and is shown to still produce useful results.

This paper appears in Transportation Research Record No. 1804, Transportation Data and Information Technology Research.

English

p. 1-7

2002

Transportation Research Record

0309077303

Figures (7) ; References (16) ; Tables (2)

Data collection; Field studies; License plates; Statistical analysis; Travel time

Data and Information Technology; Highways; Planning and Forecasting; I72: Traffic and Transport Planning

TRIS, TRB, ATRI

Dec 10 2003 12:00AM

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