east[i]

East coordinate of node

north[i]

North coordinate of node

frequency[i]

Number of times node must be visited (1 for every other day, 2 for every day)

requirement[i]

Collection requirement of node (in 1,000 litres)

distance[i,j]

Distance between nodes and (in miles)

distance_scale

Distance scale

num_days

Number of days in planning horizon

capacity

Capacity of the lorry (in 1,000 litres)

depot

Node number of depot

num_subtours

Number of subtours in current formulation

iter

Iteration number for each round of subtour elimination constraints

num_components[d]

Number of connected components in solution for day

component_id[i]

Connected component containing node

ci,cj

Dummy indices for members of COMPONENT_IDS