Event definitions and summary statistics in published Northern Corridor transit time reports
Ruth Shallom
- Published
- 20 October 2026
- Version
- v2
- Status
- Not independently peer reviewed
Abstract
Comparisons of corridor transit times are meaningful only when reports measure the same interval and use the same summary statistic. This documentary audit reviews four Northern Corridor Transit and Transport Coordination Authority reports covering January 2025 through June 2026. All four cite RECTS, yet describe four different event boundaries. The January to June 2025 report gives medians, while the other three report averages. Taken together, the reports do not establish a harmonized time series. Differences across these tables should not be read as operational change without confirmation of a common definition and aggregation method. This review examines published descriptions, not underlying trip records. The reports provide no route level counts or uncertainty intervals alongside the selected values.
Scope & limitations
This is a focused, single-reviewer documentary audit. Differences in report wording do not establish that operational definitions or data-processing rules changed. No trip-level records, route sample counts or uncertainty intervals were available.
Data & supporting files
The original Zenodo ZIP contains the manuscript, extracted report data in CSV format and a README. The searchable PDF is an additional full-text copy.
Cite this preprint
Open access under CC BY 4.0. This is an author-hosted access copy of the existing preprint.