Siting road maintenance depots. This model was applied in Victoria Province, Australia, by...

Siting road maintenance depots. This model was applied in Victoria Province, Australia, by G. Rose, D. Bennett, and D. Chippcrfield.

Historically, the system of road maintenance depots in Victoria was expanded depot at a time as needs for pavement repair, drainage works upkeep, litter collection, and so on increased 011 rural roads. Road maintenance patrols, stationed at the depots, traveled to assigned road segments for such management activities.

Vic Roads, Victoria's road authority, wanted to see if the depot system could be consolidated into fewer depots more strategically located without a loss of service efficiency. The authority hired BTA Consulting, which built a model to examine possibilities for consolidation.

First, the road system in about one-fifth of the state was divided into segments that were indexed by i Levels of maintenance activity or need for service trips based on traffic volume were calculated for each segment. Eligible depot locations were then identified: these included 19 existing depots and 15 towns with sufficient population and community structured to support a depots. A 60-minutes service time standard was utilized, An integer programming model was constructed to maximize the segments weighted by their needed trips for service that could be covered by various reduced numbers of deposits. It was found that crews fom 12 well-placed depots could cover all segments within the time standard and that as few as 9 depots archicved 94% coverage.

The model that Rose et al, applied resembled the location set covering problems diseased in the chapter. Its destination. Variables, and parameters include.

j,n = index and total number of potentials depot sites,

i.m = index and total number of demand segments;

Iji = The shortest time frm the potential depot site at j to segment i:

S = a time standard 60 minutes each segment should have a depot from which a crew can reach the segment within this time:

Ni = {set of depot sites eligihle hy! virtue of time' to cover segment j}

= {j|tji ≤ |S} = {those j such that the lime from ito i is less equal 10 8}: and

Xi = it is 1 if u depotis placed at j and 0 otherwise.

In addition. VOlI will need three new definitions:

m, =: maintenance need of road segment i (known):

Yi = 1,0; a decision variable that is 1 if road segment i is covered and 0 otherwise; and

D = maximum number of depots to be sited.

With these definitions and variables, structure a problem that maximizes the activitv weighted segments that can be covered in 60 minutes hy D depots, as Rose et al. did.