Heavy haul and over-dimensional carriers operate under some of the most complex temporal and spatial constraints in trucking. Unlike standard dry-van or reefer operations that rely primarily on hours-of-service and basic routing, permitted loads must simultaneously satisfy state-specific daylight travel windows, nighttime curfews, bridge and overhead clearance restrictions, pilot car escort availability, and law enforcement escort scheduling. Strong Tower Consulting builds algorithmic solvers that transform these interdependent rules into executable, optimized dispatch plans.
- State curfews become temporal windows attached to graph edges, so prohibited night segments are pruned automatically.
- A time-expanded graph treats every node as a place and a time window, not a place alone.
- Bridge permits, overhead wire notifications, and utility approvals are hard constraints that prune the graph further.
- Pilot cars and police escorts are scarce resources scheduled as a vehicle routing problem with time windows.
- Routes return to Truckmate, McLeod, or TMW as standard load segments, so settlement and accounting stay intact.
State-by-State Curfew Rules as Temporal Constraints
Each state maintains its own matrix of travel windows for loads exceeding legal dimensions. For example, many Midwestern states prohibit movement of loads over 14 feet wide between sunset and sunrise, while certain Southern corridors allow night moves only with additional escorts. These rules are not static; they vary by route, load configuration, and permit type (routine, superload, or mega-load).
Our constraint engines encode every state rule as a set of temporal windows attached to graph edges. When a carrier runs a multi-state superload from Minnesota to Texas, the solver must prune any route segment that would place the load in a prohibited nighttime window in Iowa, Missouri, or Oklahoma. The resulting feasible path respects all curfews without manual trial-and-error.
Multi-State Permit Route Graph Pruning
Traditional truck routing engines such as PC*Miler or Google OR-Tools solve shortest-path problems on static graphs. Heavy haul routing requires dynamic graph pruning based on time-dependent constraints. Our architecture builds a time-expanded graph where each node represents not only a geographic point but also a specific time window.
Bridge permits, overhead wire notifications, and utility company approvals are treated as hard constraints that further prune the graph. The solver returns only those routes that satisfy every permit condition while minimizing total transit days and escort costs.
Each node pairs a location with a time window. An edge survives only when every state rule and permit condition holds for the whole segment.
node = (location, time window)
edge (a, t) -> (b, t + travel_time) kept only if [t, t + travel_time] is inside the state travel window for the load width and permit type
edge removed if bridge permit, overhead wire notification, or utility approval is missing
minimize total_transit_days + escort_cost over remaining paths
| State | Max Width | Daylight Only Rule | Night Move Allowed | Escort Requirement (Over 16 ft) |
|---|---|---|---|---|
| Minnesota | 14 ft 6 in | 30 min after sunrise to 30 min before sunset | With 2 pilot cars + police | Police escort mandatory |
| Iowa | 14 ft | Sunrise to sunset | Not permitted | 2 pilot cars |
| Missouri | 16 ft | Daylight only for superloads | With special permit | Police + 3 escorts |
| Texas | 20 ft+ | Daylight travel for loads over 18 ft | Limited night windows | TxDOT certified escorts |
Pilot Car Positioning Synchronization
Escort vehicles cannot be in two places at once. When a carrier has multiple permitted loads moving through overlapping corridors, the solver must optimize escort schedules as a resource-constrained vehicle routing problem with time windows (VRPTW). Pilot car companies are modeled as mobile resources that must arrive at pickup points before load movement begins and must remain within radio range for the entire permitted segment.
arrival(escort e, pickup point) <= movement_start(load)
distance(escort e, load) <= radio_range for the entire permitted segment
each escort is assigned to at most one load at any time
Integration with real-time telematics from both the heavy haul tractor and escort vehicles allows the system to re-optimize on the fly when a curfew window is missed due to detention or mechanical delay.
Integration with Existing TMS Platforms
Our constraint solvers are designed to augment, not replace, established trucking software such as Truckmate, McLeod, or TMW. Using SQL Server stored procedures and scheduled jobs, the engine pulls load data via EDI 204 transactions, overlays permit constraints stored in normalized tables, and writes optimized route sequences back into the dispatch board.
Driver settlement rules, fuel surcharge calculations, and detention charges are all preserved because the solver outputs standard load segments that integrate directly with your existing accounting and payroll processes. Carriers retain full control of their operational data while gaining algorithmic decision support for the most difficult segment of their business.
Implementation Architecture Overview
The system is built as a microservice layer on top of your current TMS. A PostgreSQL or SQL Server graph table stores the national highway network with attached temporal constraint tables. A custom routing engine written in Python (with OR-Tools CP-SAT solver) is built to evaluate feasible paths fast enough for dispatch use. Results are pushed back into your dispatch system via API or direct database views so dispatchers see only legally compliant, escort-synchronized routes.
Recommended
- Time-expanded graph with curfew windows on every edge
- Permits and clearances as hard constraints
- Escorts scheduled as scarce, reserved resources
Avoid
- Shortest-path routing on a static graph
- Manual trial-and-error across state curfews
- Managing curfews, escorts, and permits through spreadsheets and phone calls
Frequently Asked Questions
How does the solver handle last-minute changes to a state curfew or bridge permit?
The engine maintains a master constraint database that is updated nightly from state permit portals and manual permit analyst input. When a change occurs, any affected loads are automatically re-optimized and flagged for dispatcher review. A pilot should time re-routing runs on the carrier's own load mix to confirm they fit the dispatch workflow.
Can this system work with our existing McLeod or Truckmate dispatch software?
Yes. The architecture was specifically designed for integration with McLeod, Truckmate, and TMW. We map directly to your load, driver, and equipment tables and return suggested routes through SQL views or REST endpoints that your current dispatchers already use.
What data sources are required to run an accurate heavy haul routing solver?
Core requirements include your permit application history, state-specific curfew matrices, current escort vendor contracts, bridge and overhead clearance databases, and real-time GPS from both power units and pilot cars. We help carriers consolidate these sources into a single operational data store.
How does the system account for police escort availability?
State trooper and local law enforcement schedules are modeled as limited resources with known shift patterns. The solver treats police escorts as scarce assets that must be reserved in advance, automatically generating escort request forms and integrating with state permit portals where electronic scheduling is available.
From Constraint Chaos to Predictable Heavy Haul Execution
Carriers running 50 or more permitted loads per month cannot afford to manage curfews, escorts, and permits through spreadsheets and phone calls. An algorithmic routing engine that respects every temporal and regulatory constraint gives dispatch a repeatable plan. A pilot should measure on-time performance, escort deadhead miles, and permit violations against the carrier's own baseline.
Strong Tower Consulting, LLC and Exspeedite LLC are separately organized sister companies under common ownership.
Turn curfews and escorts into a plan dispatch can run.
Strong Tower Consulting provides independent systems architecture, feasibility audits, and engineering roadmaps for motor carriers and freight brokers. Contact our advisory team or call 763-244-1373 to discuss your operational data and evaluate practical implementation paths for your fleet.