Symptom
A significant difference in distance and travel time is observed between two points depending on the routing direction:
- A → B: short distance (~56 km)
- B → A: much longer distance (~97 km)
The issue occurs only when using:
routingMode=FAST
When using:
routingMode=SHORT
the results are consistent and symmetrical.
Cause
This behavior is expected and related to how the FAST routing mode works.
FAST mode optimizes travel time, not distance
The route calculation depends on multiple factors:
- Road network hierarchy
- Speed profiles per road type
- Access to major roads (highways, main roads)
- Directional constraints (one-way streets, restricted turns, entry/exit points)
The road network is not symmetrical
An optimal route in one direction is not necessarily optimal in the opposite direction.
In certain areas (e.g. urban zones, bridges, highway access points), this may result in:
- A direct route in one direction
- A longer detour in the opposite direction, which is still considered faster
This is expected behavior and not a bug.
Resolution
Adjust the routing mode according to your business needs:
Use case 1: Reliable and consistent distance
routingMode=SHORT
Use case 2: Optimized travel time (ETA)
routingMode=FAST
Practical recommendation
- Identify the business requirement:
- Distance accuracy → SHORT
- Travel time / ETA → FAST
- Avoid using FAST mode as a reference for distance
- If needed, compare both modes to validate results for your use case
Related articles
Short and Fast Routes
Short and Fast Routes - code sample
A-B Routing