Aggregating deliveries can change routes and reduce some trips, but the result depends on the distribution of destinations. The comparison should know actual routes and constraints of the recipients. The number of shipments does not describe distance, consumption or quality of service alone.
I propose to distinguish the initial path from the proposed one, maintaining the same perimeter. Any additional withdrawals and waiting times should be included. A change can improve an indicator and create work elsewhere; the assessment must retain these effects before acknowledging an overall benefit.
Imagine two deliveries that can be joined, but require a long detour. The reduction in travel may not correspond to a reduction in distance. A comparison of paths makes the choice more readable and allows you to search for alternatives relevant to the context.
The verification uses observed data after the test and checks punctuality and unfulfilled requests. To estimate emissions, appropriate data and methods are needed. Aggregation gains value when it produces a verifiable improvement of the route and remains compatible with service commitments.