Calculating last-mile capillary routes (multi-stop)

In the last mile, the same truck typically delivers to multiple destinations before returning to the distribution centre. GLEC defines how to measure distance for this type of route.

The typical situation

A truck leaves a distribution centre and delivers to 4 different destinations before returning.

         Centre (Origin)
            |
            ↓
         Stop A (30 km from centre)
            |
            ↓
         Stop B (50 km from centre)
            |
            ↓
         Stop C (70 km from centre)
            |
            ↓
         Stop D (90 km from centre)
            |
            ↓
         Returns to Centre

The problem: which distance to measure?

Option A: What the vehicle actually travels

The truck follows a sequential route:

Leg	Actual distance
Centre → A	30 km
A → B	25 km
B → C	22 km
C → D	18 km
D → Centre (empty return)	85 km
Total actual vehicle distance	180 km

Option B: Straight-line origin-to-destination distance (SFD)

The direct linear distance is calculated for each unit from origin to its destination:

Unit	Distance calculated
Unit A	Centre → A = 30 km
Unit B	Centre → B = 50 km
Unit C	Centre → C = 70 km
Unit D	Centre → D = 90 km
Total distance	240 km

Which is “correct”?

Both are valid — but they measure different things:

Method	What it measures	When to use it
Actual legs	The real effort of the vehicle carrying that unit	When you have exact route data
SFD (straight-line direct distance)	The customer’s “responsibility” for their shipment	When you do NOT have exact route data

Is Option B valid for verification?

Aspect	Assessment
Is it valid under GLEC?	Yes, it is a permitted method
Is data quality optimal?	It can be improved
Would it pass verification?	Yes, but with a “secondary data” note

Why it is acceptable:

• Emissions are assigned proportionally to each customer/unit.
• SFD distances (Shortest Feasible Distance) are used as per GLEC — the COFRET method assigns each unit the direct distance from its origin to its destination.
• The methodology is consistent and documentable.
• In the absence of precise data, the “worst case” is chosen (conservative overestimation).

The error in total distance

In the example above:

Concept	Value
Sum of straight-line distances (Option B)	240 km
Actual vehicle distance (Option A)	180 km
Difference	+60 km (+33%)

Option B overestimates total distance because distances that “overlap” in reality are summed separately.

The effect on Unit B

Method	Distance used for tkm calculation	Calculation (if it weighs 1 tonne)
Actual legs	Centre→A + A→B = 30 + 25 = 55 km	1 t × 55 km = 55 tkm
SFD (straight-line direct distance)	Centre→B direct = 50 km	1 t × 50 km = 50 tkm

The straight-line origin-to-destination distance slightly underestimates individual tkm (10% less in this example), but it is the standard GLEC method when exact route data is unavailable.

The practical problem of splitting emissions

If you use actual legs, Unit B “pays” for the detour the truck makes to deliver to Unit A first. That is why GLEC accepts the straight-line origin-to-destination distance: it assigns each customer the minimum distance needed for their shipment, without penalising them for the route the carrier chooses.

Does empty return only count for owned vehicles?

Vehicle type	How empty return is counted
Own fleet	You calculate it with your actual km or fuel data
Subcontracted	Already included in the GLEC emission factor

How to improve data quality for subcontracted carriers

Level 1: Easy

Action	Improvement
Use the TOC specific to the actual vehicle	More precise factor than “generic average”
Confirm the fuel type	Diesel, LNG, electric… changes the factor

Level 2: Medium

Action	Improvement
Request actual km for each route	Replaces origin-to-destination with real data
Know the stop sequence	Lets you apply leg-based allocation

Level 3: High (primary data)

Action	Improvement
Actual fuel consumption per route	Real emissions, not estimated
Carrier holds GLEC certification	Their data already comes validated
Access to shared GPS or telematics	Automatic exact distances
Route optimisation software	Automatic data for each leg