Rest Stops

SALLY automatically inserts rest stops into routes when the HOS simulation detects that a driver cannot legally complete a segment. This page explains how rest decisions are made and how they appear in route plans.

How Rest Insertion Works

During route planning, the HOS simulation walks through each segment tracking the driver’s:

11-hour drive clock — Maximum continuous driving time
14-hour on-duty window — Maximum time from start of duty to end of driving
8-hour break rule — 30-minute break required after 8 hours of driving
70-hour cycle — Maximum on-duty hours in 8 days

When the simulation detects that hours_remaining < hours_needed for the next segment, it triggers the REST Optimization Engine.

Route Planner (simulating segment)
        ↓
Detects: hours_remaining < hours_needed
        ↓
Calls: REST Optimization Engine
        ↓
Returns: Recommendation (rest type, duration, reasoning)
        ↓
Route Planner: Inserts rest segment into route

Rest Types

Type	Duration	Effect	When Used
Full rest	10 hours	Resets 11h drive clock AND 14h duty window	Duty window expired, or drive clock insufficient for remaining route
Partial rest (sleeper berth)	7h or 8h	Sleeper berth split provision (7/3 or 8/2 split)	Driver in sleeper berth, partial reset available
Break	30 minutes	Satisfies 8h break requirement	After 8 hours of continuous driving

REST Optimization Engine

The REST Optimization Engine is a component called internally by the route planner. It evaluates the situation and recommends the best rest strategy.

API (Internal)

POST /api/v1/rest/recommend

This endpoint is called by the route planner, not directly by clients.

Request

{
  "current_location": {
    "latitude": 35.3733,
    "longitude": -119.0187,
    "name": "After Stop A"
  },
  "driver_state": {
    "hours_driven": 8.0,
    "on_duty_hours": 10.0,
    "hours_since_break": 8.0,
    "cycle_hours_used": 45.0
  },
  "dock_duration_hours": 0,
  "remaining_route_hours": 6.5,
  "is_dedicated_rest_stop": true
}

Response

{
  "recommendation": "FULL_REST",
  "duration_hours": 10,
  "confidence": 1.0,
  "feasibility": "NOT_FEASIBLE",
  "reasoning": "Mandatory rest required. HOS 14h duty window will be exceeded before reaching next stop. Full rest resets both drive clock (11h) and duty window (14h).",
  "opportunity_score": null,
  "rest_location": {
    "name": "Truck Stop - Exit 45",
    "latitude": 35.3801,
    "longitude": -119.0429,
    "type": "truck_stop"
  }
}

Recommendation Categories

Mandatory Rest (Confidence: 100%)

The route is not feasible with current hours. The driver must rest.

Triggers:

Drive clock insufficient for next segment
Duty window will expire before segment completion
Cycle hours approaching 70h limit

{
  "recommendation": "FULL_REST",
  "confidence": 1.0,
  "feasibility": "NOT_FEASIBLE",
  "reasoning": "Mandatory rest required. Driver has 2h drive time remaining but next segment requires 4h."
}

Opportunistic Rest (Confidence: 60–75%)

The route is feasible but marginal. Dock time is available and could be leveraged for rest.

Triggers:

Long dock time at next stop (3+ hours)
Driver’s hours are getting low but technically sufficient
Extending dock time to 7–10h provides significant hour recovery

{
  "recommendation": "PARTIAL_REST",
  "confidence": 0.7,
  "feasibility": "FEASIBLE_BUT_TIGHT",
  "reasoning": "Opportunistic rest recommended. Dock time of 4h at Stop B could be extended to 7h partial rest, recovering 7h of drive time for remaining route.",
  "opportunity_score": 72
}

No Rest Needed

The driver has sufficient hours to complete the remaining route.

{
  "recommendation": "NO_REST",
  "confidence": 1.0,
  "feasibility": "FEASIBLE",
  "reasoning": "Driver has 8.5h drive time remaining. Remaining route requires 5.2h. No rest needed."
}

Rest Segments in Route Plans

When a rest stop is inserted, it appears as a segment in the route plan:

{
  "sequence": 7,
  "type": "rest",
  "location": "TA Travel Center - Fresno",
  "rest_type": "full_rest",
  "duration_hours": 10.0,
  "reason": "HOS 14h duty window approaching. Full rest required to continue safely.",
  "hos_state_after": {
    "hours_driven": 0.0,
    "on_duty_hours": 0.0,
    "hours_since_break": 0.0,
    "drive_hours_remaining": 11.0
  }
}

Key fields:

Field	Description
`rest_type`	`full_rest`, `partial_rest`, or `break`
`duration_hours`	How long the rest lasts
`reason`	Human-readable explanation of why rest was inserted
`hos_state_after`	HOS state after rest completes (clocks reset for full rest)

Decision Factors

The REST Optimization Engine considers these factors when making a recommendation:

Factor	Weight	Description
HOS feasibility	Highest	Can the driver legally complete the remaining route?
Hours remaining	High	How close is the driver to HOS limits?
Remaining route demand	High	How many driving hours does the rest of the route require?
Dock time availability	Medium	Is there dock time that could double as rest?
Cost (extra time)	Medium	How much total time does inserting rest add?
Opportunity score	Low	Composite score (0–100) for opportunistic rest

FMCSA Rules Reference

Rule	Limit	Reset Mechanism
Daily drive time	11 hours	10h consecutive off-duty (full rest)
Daily on-duty window	14 hours	10h consecutive off-duty (full rest)
Break requirement	30 min after 8h driving	Any 30-min off-duty or sleeper berth period
Cycle limit	70 hours / 8 days	34-hour restart, or daily recap (oldest day drops off)
Sleeper berth split	7/3 or 8/2 split	One period in sleeper berth, other off-duty

SALLY enforces all of these rules. Routes with zero violations are guaranteed.