Random Faults
When a random fault occurs, the truck can progress through up to four response phases. Each phase can be enabled or disabled independently, and the truck performs the enabled phases in sequence.
The phases are evaluated in the following order:
| Phase | Purpose |
|---|---|
| Phase 1 – Immediate Stop and Potential Rescue | Immediately identifies the random fault, stops the truck where required, and applies any configured rescue waiting behaviour. |
| Phase 2 – Roadside Fix | Stops the truck for a roadside repair duration, either while blocking traffic or at a location where other trucks can pass. |
| Phase 3 – Dump Payload | Directs a loaded truck to unload its payload at an allowed destination. |
| Phase 4 – Workshop Fix | Directs the truck to a selected workshop and applies the configured workshop repair duration. |
The truck proceeds through each enabled phase in order. Disabled phases are skipped.
Once all enabled phases have been completed, the truck returns to its normal task and operating behaviour.
Important Phase Behaviour
Phase 1 can be enabled without enabling Phases 2, 3, or 4. However, Phase 1 primarily represents the immediate handling of the random fault and any required rescue period.
If only Phase 1 is enabled, the truck may appear to resume travelling immediately when no rescue or subsequent repair phase is required. The random fault is still generated and can be confirmed in the simulation log.
Therefore, to model a truck that remains stopped for a defined repair duration, enable:
- Phase 1 and Phase 2, or
- Phase 2 only, depending on whether the truck must stop immediately when the fault occurs.
Later phases do not require every previous phase to be enabled. For example:
- Phase 1 and Phase 4 may be enabled while Phases 2 and 3 are disabled.
- Phase 3 and Phase 4 may be enabled without Phase 2.
- Phase 4 may be enabled by itself.
The truck will skip disabled phases and proceed to the next enabled phase.
At least one response phase must be enabled when random faults are being modelled.
Phase 1 – Immediate Stop and Potential Rescue
Phase 1 represents the initial response when the random fault is triggered.
| Property | Description |
|---|---|
| Enable (Immediately Stop Truck) | When enabled, the truck handles the fault immediately at or near its current location rather than continuing directly to a later enabled phase. |
| Wait for Rescue If Needed Duration (seconds) | Defines how long the truck waits for rescue or assistance when rescue is required. |
| Passing Mode While Waiting for Rescue | Defines how surrounding traffic behaves while the truck is stopped and waiting for rescue. |
Phase 1 Behaviour
Phase 1 can run without any later phase. However, if no rescue is required and no other phase is enabled, there may be no extended activity to keep the truck stopped. In this situation, the truck can resume travelling immediately after the fault is handled.
This means that Phase 1 should not be used by itself when the intended behaviour is for the truck to remain stopped for a fixed repair duration. Enable Phase 2 and configure its roadside-fix duration to model that behaviour.
Random fault events can be confirmed by searching the simulation log for entries relating to random faults.
Passing Modes While Waiting for Rescue
| Passing Mode | Description |
|---|---|
| Disabled | No special passing behaviour is applied. Other trucks may remain blocked depending on the road geometry and the stopped truck’s location. |
| Stop & Wait Then Pass Through | Approaching trucks stop and wait until they can safely pass through the affected area. |
| Drive Around On Two Lane, Otherwise Block | Other trucks may pass around the stopped truck when a suitable two-lane or multi-lane section is available. Where passing is not possible, traffic remains blocked. |
When the truck is stopped in a location where traffic cannot safely pass, such as:
- a single-lane road,
- a terminal,
- an intersection,
- a passing bay, or
- another constrained location, other trucks may queue behind it.
Phase 2 – Roadside Fix
Phase 2 models a repair performed at or near the fault location without immediately sending the truck to a workshop.
| Property | Description |
|---|---|
| Enable | Enables the roadside-fix phase. |
| Roadside Fix Duration (seconds) | Defines how long the truck remains stopped while the roadside repair is performed. The value may be fixed or selected from a configured distribution. |
| Do Not Block Traffic | When enabled, the truck attempts to perform the roadside fix at a suitable location where other trucks can pass. |
| Passing Mode During Roadside Fix | Defines how traffic behaves while the roadside repair is being completed. |
Relationship Between Phase 1 and Phase 2
Phase 2 provides the repair duration that keeps the truck stopped.
For example, to model a truck that:
- Stops immediately when the fault occurs.
- Blocks or affects traffic.
- Remains stopped for a defined duration.
- Then resumes normal operation.
Enable both Phase 1 and Phase 2.
Configure Phase 2 with:
- the required roadside-fix duration;
- the appropriate passing mode; and
- traffic blocking enabled or allowed, depending on the intended behaviour.
If Phase 1 is disabled but Phase 2 is enabled, the truck may continue travelling until it reaches a location suitable for the configured roadside-fix and passing behaviour.
If Phase 1 is enabled and the truck cannot safely perform the roadside fix at its immediate location, the truck may complete the Phase 1 rescue period and then move to a more suitable location before beginning Phase 2.
Traffic Behaviour During a Roadside Fix
Where a suitable two-lane or multi-lane road section is available, passing behaviour may allow other trucks to travel around the stopped truck.
Traffic using the remaining lane may operate as a temporary bidirectional section. Trucks travelling in opposite directions may need to stop and take turns before entering the affected section.
Trucks already travelling toward the affected road may be rerouted where the network geometry permits.
When the stopped truck is ready to resume travelling, it may delay restarting until trucks currently passing it have cleared the affected section.
If the truck is too close to the start or end of a multi-lane section, or there is insufficient space to create a safe passing route, the truck may instead stop and block traffic.
Phase 3 – Dump Payload
Phase 3 controls whether a loaded truck unloads its material before proceeding to a workshop or completing the remaining fault-response sequence.
| Property | Description |
|---|---|
| Enable | Enables payload dumping as part of the random-fault response. |
| Destinations | Defines the destinations that may receive the truck’s payload. These may include the original task destination or other selected dump and stockpile destinations. |
When multiple destinations are available, the truck may travel to the closest valid destination selected by the user.
The fault-response destination may override the destination originally assigned by the truck’s task.
If the truck is empty, no payload-dumping activity is required and the truck proceeds to the next enabled phase.
If Phase 3 is disabled but Phase 4 is enabled, a loaded truck may travel to the workshop while still carrying its payload. After completing the workshop fix, it proceeds to its original scheduled destination to unload before returning to normal operation.
Phase 4 – Workshop Fix
Phase 4 represents a fault that requires the truck to travel to a workshop.
| Property | Description |
|---|---|
| Enable | Enables workshop repair as part of the fault-response sequence. |
| Workshop | Selects the workshop, or workshop subset, that may receive the faulted truck. |
| Fix Duration (seconds) | Defines how long the truck remains at the workshop while the repair is completed. The duration may be fixed or selected from a configured distribution. |
When this phase begins, the truck travels to the selected workshop and remains there for the configured fix duration.
After the workshop fix is completed:
- an empty truck returns to normal operation;
- a loaded truck that has already completed Phase 3 returns to normal operation; or
- a loaded truck that skipped Phase 3 travels to its original scheduled destination to unload before returning to normal operation.
Phase Selection and Skipping Rules
The fault-response sequence depends on which phases are enabled and where the truck is located when the fault occurs.
Only Phase 1 Enabled
The truck handles the immediate random-fault event. However, if no rescue or additional activity is required, it may resume travelling immediately.
Use Phase 1 together with Phase 2 when the truck must remain stopped for a specified duration.
Phase 1 and Phase 2 Enabled
The truck stops immediately during Phase 1 and then completes the configured roadside-fix duration during Phase 2.
This configuration should be used when the truck must stop and block or affect traffic for a defined period.
Phase 1 Disabled and Phase 2 Enabled
The truck does not necessarily stop at the exact location where the fault is triggered. It may continue travelling until it reaches a location suitable for the roadside fix and the configured passing behaviour.
Truck Already in a Suitable Multi-Lane Location
Where the truck is already in a suitable two-lane or multi-lane location when the fault occurs, the simulation may proceed directly to the passing or roadside-fix behaviour rather than applying a separate traffic-blocking stop.
No Suitable Stopping Location
If the enabled phase requires a specific road condition and no suitable location is available, the truck may continue travelling until the required condition is met.
Where only a location-dependent phase is enabled, it is possible for the visible stop behaviour to be skipped if no valid location is encountered.
Example Fault Workflows
Immediate Stop Followed by a Roadside Fix
- A random fault is triggered.
- Phase 1 stops the truck immediately.
- Other trucks block, wait, or pass according to the selected passing mode.
- Phase 2 keeps the truck stopped for the configured roadside-fix duration.
- The truck resumes its normal task.
Full Four-Phase Response
When all four phases are enabled:
- The truck handles the immediate stop and any required rescue period.
- It completes a roadside fix at the fault location or at a suitable passing location.
- If loaded, it travels to an allowed destination and dumps its payload.
- It travels to the selected workshop.
- It remains at the workshop for the configured fix duration.
- It returns to normal operation.
Workshop Fix Without Payload Dumping
When Phase 3 is disabled and Phase 4 is enabled:
- The loaded truck travels directly to the workshop.
- It remains there for the configured workshop-fix duration.
- It then travels to its original scheduled destination.
- It unloads the payload.
- It returns to normal operation.
Recommended Configuration for a Timed Random Stop
To model a random event where the truck stops and blocks traffic for a defined period:
- Enable Phase 1 – Immediate Stop and Potential Rescue.
- Enable Phase 2 – Roadside Fix.
- Set the Phase 1 rescue duration as required.
- Set the Phase 2 roadside-fix duration to the required stop time.
- Configure the Phase 2 passing mode to allow or prevent passing.
- Leave Phases 3 and 4 disabled unless payload dumping or workshop repair is also required.
This configuration ensures that the fault is triggered immediately and that the truck remains stopped for the required period rather than resuming travel immediately.