Tolerance Window Analysis

Key Finding

By using the existing tolerance windows (min planned to max planned) to consolidate visits, 73% of location visits could be eliminated — reducing from 4,226 visits down to 1,121 across the year.

This means the same team is currently scheduled to visit the same location on average 3-4 separate days when, within the allowable maintenance windows, all that work could be batched into fewer visits.

Current vs Optimised Visits

Metric Current Optimised Saving
Total location visits (group+location+day) 4,226 1,121 3,105 (73%)
Unique group+location combos with savings 268

Savings by Depot

Depot Current visits Optimised Saved % reduction
Flinders Street 571 121 450 79%
Clifton Hill 456 129 327 72%
Newport 424 98 326 77%
Carrum 395 119 276 70%
East Malvern 377 101 276 73%
South Kensington 377 108 269 71%
Sunshine 335 71 264 79%
Ringwood 330 81 249 75%
Dandenong 316 77 239 76%
Caulfield 274 89 185 68%
North Melbourne 192 39 153 80%
Spencer Street 101 17 84 83%
MURL 14 7 7 50%

Worst Examples

The most extreme cases of repeated visits to the same location by the same team:

Work Group Location Current visits Could be Saved WOs
Flinders Street 1203 Flinders St A 89 11 78 418
Spencer Street 1101 Southern Cross 87 9 78 316
Flinders Street 1201 Flinders St E 85 8 77 287
Newport 2201 Newport 80 10 70 300
North Melbourne 1302 North Melbourne 73 10 63 291
Dandenong 4301 Westall 71 9 62 333
Clifton Hill 3301 Epping 68 10 58 254
Ringwood 3201 Box Hill 35 5 30 115

For example, Flinders Street Section 1203 visits Flinders St A 89 separate times across the year to do 418 work orders. By batching work within the tolerance windows, this could be reduced to just 11 visits.

How This Works

Each work order has a maintenance window defined by min_planned (earliest permissible start) and max_planned (latest permissible completion) as provided in the source data. The planned date currently sits at the midpoint of this window — consistent with system-generated scheduling from the ERP with no manual geographic optimisation applied.

The analysis uses a greedy merge approach: starting with the earliest visit, it checks whether the next visit's maintenance window overlaps. If it does, both visits could be done on a single trip to that location. This continues until no more merges are possible, at which point a new visit is required.

Why Reducing Trips Matters

The scheduled work orders are predominantly inspections. When a team inspects an asset, they will often identify and carry out corrective work on the spot — adjustments, cleaning, minor repairs. This means a team visiting a location for 3 scheduled inspections may spend half a day there doing the inspections plus follow-up work.

Sending a team back to the same location the following day for 1 more inspection wastes a full return trip when that inspection could have been added to the previous visit with negligible additional time. The inspection itself may take 30 minutes, but the trip to get there and back, the access arrangements, and the administrative overhead represent a far greater cost.

Important Caveats

  1. Daily workload limits not modelled — batching all work at a location onto fewer days increases the work per visit. The practical limit depends on job durations (not available in this dataset) and the volume of corrective work arising from inspections. Actual labour hours have been requested from GPM.

  2. The 73% figure is a theoretical maximum — applying practical capacity constraints would reduce this, but even a conservative 30-40% reduction in visits would represent a significant efficiency gain.

  3. Travel time savings compound — this analysis only counts visit reduction within a single group+location. When a team eliminates a trip to one location, that day's travel to other locations is also avoided.

Implication

Each unnecessary visit to a location represents a return trip from the depot, access and protection arrangements, work pack administration, and team mobilisation. By batching work within existing maintenance windows, a significant proportion of these trips could be eliminated without any change to the maintenance standard or compliance requirements — work is simply done earlier or later within the allowable window to coincide with other work at the same location.