I'd also like to challenge the notion that the earlier Green Line shutdowns are ineffective or resulted in almost no time savings:
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During the most recent shutdown, highlighted in red, this section (Copley to Haymarket) only has the E branch running as opposed to all 4 branches. There seems to be a notable reduction during this period. This seems to suggest that the lack of travel time reductions during earlier periods may be more of a result of congestion in the Central Subway and irregularities, as opposed to speed restrictions.
The opposite direction (Haymarket to Copley) is not nearly as notable during this period, though there still seems to be a slight reduction. However, note that dwell times have increased in both directions (likely due to the higher load per vehicle), which may offset the faster trips between stations. This direction also still has a slow zone around Haymarket.
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