Split-Sleeper HOS Optimization in Algorithmic Dispatch

This page is the split-sleeper specialty under Predictive Dispatch Constraint Solving. It does not restate the general catalog of hard and soft constraints. It specifies the state, the two named pair shapes, the 14-hour exclusion arithmetic, the telematics contract, and the abort rule a dispatch solver needs before it may even offer a split. Read Carrier AI Readiness Evaluation if the fleet has not yet named who may accept a machine recommendation.

Why a 10-hour sleeper reset strands home time

A solver that knows only one rest primitive will schedule a single block of at least 10 consecutive hours off duty or in the sleeper berth. That block is a real reset shape, and many plans should keep it. It is a poor model of a property-carrying driver who can lawfully split the 10 hours into two qualifying periods. The 10-hour-only search either inserts the full block before the next appointment, which pushes the domicile arrival past the published home-time window, or it sends the driver home early and drops the load that a qualifying pair could have covered. Home time then shows up as a large soft penalty even when a legal pair existed on the clock.

Home time in this design is a published soft penalty: minutes between the planned arrival at the domicile terminal and the driver's home window, multiplied by a weight the operations manager sets in advance. It is not a hard constraint, and it never outranks hours of service. The split model adds two discrete rest shapes so the search can test whether a short off-duty period and a later sleeper reduce that penalty without breaking a hard clock. If the driver record says split_allowed is false, the solver ignores both shapes and behaves as the 10-hour model for that person. A preference flag is a decision right, not a penalty the optimizer is free to buy out.

Confirm 49 CFR 395.1(g) before anyone uses the model

This is a planning model, not legal advice. Before a carrier turns the choice on, counsel or the safety manager should confirm the current text of 49 CFR 395.1(g), including any guidance the carrier already follows. The shape encoded here is the property-carrying split used for planning: two periods that total at least 10 hours, one of them at least 7 consecutive hours in the sleeper berth, the other at least 2 consecutive hours off duty and/or in the sleeper berth. Operations commonly call the scheduled pairs 7/3 and 8/2. Both qualifying periods are excluded from the 14-hour window. The solver recomputes the 14-hour window from the end of the first qualifying period.

The page does not describe enforcement, roadside conversation, or any method of evading hours of service. If the engine and the regulation disagree, the plan stops. Passenger-carrying rules, adverse-driving exceptions, and short-haul exceptions are out of scope. The tractor master must show has_sleeper_berth true before a long period can be proposed. A day cab cannot host a 7-hour sleeper period, and the solver must not relabel off duty as sleeper to pass the test.

Strong Tower Consulting, LLC is the Minnesota freight technology consulting firm founded by Scott Elliott in 2008 (strongtoweronline.com). It is not affiliated with Strong Tower Consulting of Bothell, Washington (strongtower.consulting or strongtower.ai).

State variables the solver must carry

Every candidate is a function of a snapshot, not of a live keystroke on the dispatch board. The minimum state is remaining drive, the 14-hour anchor, the start and end of each sleeper or off-duty period under test, duty status, and an as-of timestamp. Remaining drive is an integer number of minutes from the hours-of-service engine. The solver may display it as hours and minutes. It may not recompute it from raw GPS speed. The 14-hour anchor is a timestamp. After a qualifying pair, that anchor is the end of the first qualifying period. Before a pair qualifies, the anchor stays where the engine put it.

Duty status is a closed enumeration: OFF_DUTY, SLEEPER_BERTH, DRIVING, ON_DUTY_NOT_DRIVING. Anything else, including a blank or a vendor-specific code without a signed crosswalk, is UNKNOWN_DUTY_STATUS and aborts the recommendation. The sleeper-period start and end are timestamps with a duration in whole minutes. Seven hours is 420 minutes. A period of 419 minutes fails the long-side test. The as-of timestamp is the moment the clocks, the duty status, and the position were mutually consistent. It is not the time a file landed in an inbox. Store it in UTC. Convert to terminal local time only for the screen.

7/3 and 8/2 as discrete choices

The search offers two named choices. A dispatcher does not type a custom duration on a live load. A 7/3 candidate is at least 420 minutes in the sleeper berth plus at least 180 minutes off duty and/or in the sleeper, total at least 600. An 8/2 candidate is at least 480 minutes in the sleeper plus at least 120 minutes off duty and/or in the sleeper, again at least 600. Either period may occur first. The first qualifying period is the one that ends earlier, not the longer one.

Pairs outside those two names can still meet the regulatory minimums, for example 9 hours in the sleeper and 2 hours off duty. They are not on the default menu. A 7-hour sleeper plus a 2-hour off-duty period totals 9 hours and does not qualify. The solver must not exclude either period and must not move the 14-hour anchor. A 7-hour off-duty period that never enters the sleeper berth does not satisfy the long side.

Rolling 14-hour exclusion arithmetic

Exclusion is a subtraction of qualifying rest from the 14-hour window, not a gift of new driving time. Once both periods qualify, every minute inside either qualifying period is left out of the 14-hour sum. The new window is measured from the end of the first qualifying period. On-duty time after that instant counts. The second qualifying period does not count. Time before the first qualifying period is not pulled back into the new window. If the pair later fails because a recorded period was shorter than the plan, the exclusion is void and the anchor returns to the engine's unpaired value on the next snapshot.

Work the minutes as integers. Let F be the end of the first qualifying period and S be the end of the second. Let Q2 be the duration of the second qualifying period. Counted minutes equal (S minus F) minus Q2, converted to minutes, minus nothing else unless the engine also excludes a status this page does not model. Remaining 14-hour minutes equal 840 minus counted minutes, and never below zero in a feasible plan. Overlap between the two periods is a data error, not a clever compression. The solver rejects overlap before it does the subtraction. Durations are not rounded up to the next hour to make a 9-hour pair look like 10.

Illustrative timeline of one qualifying pair

The clocks below are illustrative planning figures. They are not a driver's log, not a result from a fleet, and not a template to copy onto an electronic logging device. They exist so a builder can see the anchor move. The carrier's own engine would still have to return the same structure before a dispatcher could accept a plan like it. Local times are used only in the table. Storage remains UTC.

At 23:00 both periods qualify. The first qualifying period ended at 11:00, even though it is the shorter one, so the 14-hour anchor moves to 11:00. From 11:00 to 16:00 is 5 hours on duty, which counts. From 16:00 to 23:00 is 7 hours in the sleeper, which is excluded. Illustrative remaining 14-hour window: 9 hours. Remaining drive stays a field the engine must supply. A 10-hour-only model starting the sleeper at 16:00 would hold until 02:00 and would not run this exclusion.

Hard clocks the split does not erase

The ordinary 11-hour driving limit remains. Nothing in the pair sets remaining_drive_minutes to 660. Driving before the short period, between the periods, and after the long period is legal only if the engine still shows minutes left at each of those points. The planner's job is to refuse a candidate the engine marks noncompliant. It is not to discover a larger driving budget than the engine published on the same as-of timestamp.

The 30-minute break remains hard. break_drive_minutes is driving since the last interruption of at least 30 consecutive minutes. A candidate that reaches a dock or a proposed rest with that clock already in breach is infeasible, even when the pair totals 10 hours. The cycle remains hard. The carrier assigns 60 hours in 7 days or 70 hours in 8 days. Sleeper and off duty do not raise that ceiling. On-duty minutes still accrue. A pair that breaks the cycle is rejected with reason CYCLE.

Telematics ingestion contract

The feed is a contract with required fields, not a screen scrape of an hours-of-service portal. Each message carries driver_id, vehicle_id, duty_status, sleeper_berth_flag, event_time, as_of_ts, remaining_drive_minutes, fourteen_hour_anchor_ts, cycle_rule, cycle_used_minutes, break_drive_minutes, gps_lat, gps_lon, gps_fix_ts, gps_age_seconds, event_sequence, and source. sleeper_berth_flag is true only when the tractor has a sleeper and the status is SLEEPER_BERTH. The ingestion worker computes gps_age_seconds from as_of_ts minus gps_fix_ts. The browser does not subtract two local clock strings and call that an age.

Zero speed is not a sleeper. A tractor can sit at a dock, a gate, or a fuel island with status DRIVING or ON_DUTY_NOT_DRIVING. The solver places a long period only where the plan says the driver would record SLEEPER_BERTH, and only on a vehicle with has_sleeper_berth true. Yard move and personal conveyance stay on the crosswalk the safety manager has signed. The default crosswalk does not map either one onto SLEEPER_BERTH. If the vendor code is absent from the crosswalk, the message fails closed.

Clock fields are copied from the hours-of-service engine. The dispatch service may draft a 14-hour exclusion for a future pair, then it must submit that draft and store the engine receipt. The row quotes the receipt, as_of_ts, and event_sequence. A newer sequence invalidates it. If the engine disagrees with the local subtraction, the engine wins and the reason is ENGINE_MISMATCH.

Stale-clock abort rule

If the solver's run time minus as_of_ts is greater than the published stale threshold, the run aborts. No split recommendation is written. The dispatcher sees reason STALE_CLOCK and the age in seconds. They do not see a guessed remaining drive, a guessed anchor, or a "probably still legal" flag. An illustrative planning threshold is 15 minutes. That number is a starting control for a pilot, not a regulatory grace period, and the carrier can set a tighter one. Loosening it past the pilot value requires a written change, not a quiet edit on the night shift.

GPS staleness is a separate gate. If gps_age_seconds exceeds the published location threshold, an illustrative planning figure of 10 minutes, the solver may not name a rest location. A fresh clock with a stale fix is marked LOCATION_UNTRUSTED and cannot be accepted. If both gates fail, STALE_CLOCK wins and nothing is offered. Accept re-reads the snapshot and runs the same abort before it stores dispatcher_user_id.

Pairing a split with an appointment window

An appointment is window_open, window_end, and early_allowed on the shipper location. The solver tests 7/3 and 8/2 on a grid. An illustrative step is 15 minutes. Each placement checks sleeper capability, non-overlap, the 10-hour total, and the engine receipt at the dock. Arrival must fall inside the window. If early_allowed is false, early arrival is infeasible. Slack is appointment_slack_minutes on that shipper. An illustrative planning value is 30 minutes, used only when the record allows it.

If neither named pair hits the window with every hard clock intact, the result is INFEASIBLE_APPOINTMENT. The solver does not shorten the sleeper below 7 hours, shrink the total below 10, or drop the 30-minute break to save the door. A dispatcher may still build a manual plan, including a full 10-hour rest or another driver, and that plan must pass the same engine. Among feasible pairs the score is home-time penalty plus empty miles plus slack consumed. The lowest score is the recommendation. Ties break toward the sleeper that ends earlier at the domicile.

What the dispatcher must still accept

The model may recommend. It may not assign. The recommendation row carries pair_shape, rest_1_start, rest_1_end, rest_1_status, rest_2_start, rest_2_end, rest_2_status, recomputed fourteen_hour_anchor_ts, hos_engine_receipt_id, as_of_ts, and event_sequence. A named dispatcher accepts or rejects. Acceptance writes dispatcher_user_id, accepted_at, and plan_version. Rejection writes a reason from a short list: DRIVER_PREFERENCE, APPOINTMENT_RISK, WEATHER, EQUIPMENT, OTHER. Acceptance does not write a duty status to the electronic logging device and does not message the driver that the rest has already happened.

The driver records actual duty status. The next snapshot is compared with the accepted intervals. If the sleeper is short of the minimum, or the short period never occurs, the plan expires as NOT_TAKEN and the next search uses the new clocks. Nobody edits the old snapshot to make it look feasible. Team rules and any split 49 CFR 395.1(g) does not support are off by configuration. An unaccepted row drops off the board at its time-to-live. An illustrative time-to-live is 20 minutes or the next snapshot, whichever comes first.

Pilot metrics, with hard-constraint violations at zero

Pilot on one terminal or one corridor, not the network. The release gate is binary: hard-constraint violations must be zero. A violation is any accepted plan that the hours-of-service engine marks as a breach of the 11-hour driving limit, the 14-hour window, the 30-minute break, the assigned 60/7 or 70/8 cycle, or a split that fails the engine's implementation of the qualifying-pair rules. One violation stops the pilot. The response is to fix the state handoff or turn the menu off. It is not to lower a penalty weight until the violation disappears from a dashboard.

Collect the other figures and do not set a success target in advance. Count recommendations, acceptances, rejections, STALE_CLOCK aborts, LOCATION_UNTRUSTED rows, ENGINE_MISMATCH rows, and NOT_TAKEN expirations. Record solver runtime. Compare home-time minutes with the 10-hour-only plan on the same snapshot and report the distribution. An illustrative watch length is four weeks. That figure is how long to hold the gate open, not a result any fleet has already posted. If a hard-constraint violation appears, the pilot stops.

Frequently asked questions

These answers restate the planning rules above. They are not a substitute for the current text of 49 CFR 395.1(g), and they are not an instruction to the driver. If a vendor demo skips the engine receipt or the stale-clock abort, the demo is not implementing this model. The same standard applies to a spreadsheet that moves the 14-hour anchor without storing as_of_ts.

Use the answers in design reviews with safety, dispatch, and the telematics vendor in the same room. Safety owns the crosswalk and the decision to set split_allowed. Dispatch owns acceptance of each row. The vendor owns delivery of the contract fields on time. No one in that review is authorized by this page to treat a model score as compliant hours.

Published October 23, 2026 by Strong Tower Consulting, LLC. Founded 2008 in Minnesota by Scott Elliott.