The Value of Preemptive Pick-Up Services in Dynamic Vehicle Routing for Last-Mile Delivery: Space-Time Network-Based Formulation and Solution Algorithms

Table 4

Comparison between non-preemptive and preemptive service.

	Scenario 1: Non-preemptive service	Scenario 2: Preemptive service
Similarities	(i) Bellman equation-based dynamic programming procedure is used
Differences	(i) Delivery service is uninterruptible	(i) delivery service is interruptible
	(ii) Classical Bellman equation is used	(ii) Bellman equation is modified due to the division of service duration
Optimal path	Depot-1-2-3-depot	Depot-1-2-3-2-depot
Interrupt service at physical node 2?	No	Yes
Travel cost	6	7
Delivery utility	107 = 70	107 = 70
Pick-up utility	0	15
Objective function value	70 + 0–6 = 64	70 + 15–7 = 78 > 64