Why Oversize Route Planning Is Different
Standard freight routing is a logistics problem: find the fastest path from origin to destination within the carrier's network. Oversize route planning adds an engineering layer on top of the logistics layer. Every structure on the planned route must be verified against the load's weight and height. Every overhead obstruction — bridges, utility lines, traffic signals, pedestrian bridges — must be checked against the load's height with the trailer and load in transport configuration. Every narrow road or restricted corridor must be identified and avoided or explicitly permitted.
R&RM LLC has been planning and executing oversize and overweight moves across all 48 continental states since 2011. Route planning is one of the most consequential steps in a heavy haul move — a route error costs time, money, and in the worst cases causes damage to infrastructure or the load itself. This guide explains the route planning process from the carrier's perspective so shippers understand what is being done before their load departs.
Get a Quote for Your LoadStarting Point: Load Dimensions and Configuration
Width Is the Primary Routing Constraint
The most common routing constraint for oversize loads is width. Legal highway width for standard freight is 8 feet 6 inches. Once a load exceeds that, it requires a permit and triggers a series of questions: How much wider than legal limits is the load? Does the load's width trigger pilot car requirements? Does the width require a specific lane position — for example, centering the load in the lane — that affects whether narrow roads can be used?
For loads wider than 14 feet, most states require at least one pilot car. For loads wider than 16 feet, two pilot cars are generally required. At widths beyond that — 18 to 20 feet is where the most complex width restrictions begin — some states require police escort, require travel only at specific times of day, or prohibit travel on certain road classes entirely. Width also determines which bridges can be used, since some bridges have structural elements or railings that limit the usable road width below the bridge's rated capacity.
Height and Overhead Clearance
Legal height on most US highways is 13 feet 6 inches. Above that limit, the load requires a permit and the carrier must identify every overhead obstruction on the planned route. The Federal Highway Administration (FHWA) maintains a national bridge clearance database, but individual state DOTs maintain more complete records for local and state routes, and some overhead obstructions — utility lines, gantry signs, traffic signals, pedestrian walkways — are not captured in any central database.
For loads approaching or exceeding 16 feet in height, carriers typically perform a line-of-sight review of satellite and street-level imagery for the planned route, and many states require a physical route survey — a pilot car driving the route before the load departs to confirm every clearance by measuring with a height pole. A height pole is an extendable rod that replicates the load's height; the pilot car drives under each overhead obstruction and confirms clearance before the load attempts it.
Length and Overhang Restrictions
Legal trailer length and overall combination length vary by state, but most states allow combinations up to 65 feet. Loads that overhang the front or rear of the trailer beyond certain limits require specific flagging — a flag or light at the point of overhang — and may trigger escort requirements for rear overhang. Long loads and loads with significant overhang also affect turning radius, which becomes a routing consideration in urban areas and at sites with tight access.
Weight and Bridge Formula
For overweight loads, the bridge formula under 23 U.S.C. § 127 limits the weight that can be carried on a given axle group relative to the axle spacing. A load that fits within legal width and height may still be routed around certain bridges if it exceeds those bridges' weight ratings. The national bridge database maintained by FHWA provides rated capacity for most bridges, but some older bridges — especially on state highways and rural county roads — have reduced or unknown capacities that require conservative assumptions or physical route surveys.
Bridge Analysis: The Technical Core of Route Planning
How Bridge Weight Ratings Work
Every bridge on the federal-aid highway system has a sufficiency rating and a load rating. The load rating specifies the maximum weight the bridge can safely carry for two standard loading cases: inventory load rating (the weight at which the bridge can operate indefinitely) and operating load rating (the maximum weight the bridge can safely carry in a single crossing). Oversize permit routing uses these ratings — specifically the operating load rating — to determine whether a permitted combination can cross each bridge on the route.
For loads within the standard permit envelope — say, 120,000 to 150,000 pounds on a standard RGN — most bridges on interstate and primary state highways are capable of handling the load because they were designed to accommodate standard legal combinations plus a reasonable safety margin. As loads approach superload territory — 200,000 to 500,000 pounds or more — bridges must be evaluated individually, and many require detailed engineering analysis before the permit is issued.
Posting and Weight-Restricted Bridges
Posted bridges are bridges where the authorized load rating is below the standard legal limit — typically due to age, deterioration, or original design to a lower load standard. A posted bridge with a 30-ton limit cannot legally be crossed by a loaded truck with a 40-ton payload, regardless of whether the combination is technically oversize. Bridge posting data is maintained by each state DOT; some states update this data in real time while others update it on a less frequent cycle. Permit systems check posting data automatically for routes submitted through state permit portals, flagging or rejecting routes that cross posted structures.
When a posted bridge falls on the most direct route, the carrier must identify an alternate crossing — which may add significant distance if the next available crossing is 20 or 30 miles away. This is one of the reasons heavy haul moves sometimes follow what looks like an illogical route: the route is following the chain of bridges that can handle the load, not the most direct geographic path.
Superload Engineering Analysis
Loads above a certain weight threshold — generally 150,000 to 200,000 pounds gross weight depending on the state — are classified as superloads and require engineering analysis rather than automated permit issuance. The permit office submits the load data (gross weight, axle weights, axle spacings) and the proposed route to a structural engineer, who calculates the actual stress on each critical bridge structure on the route. This process can take days to weeks for complex moves and may result in the permit office requiring structural reinforcement of certain bridges, limiting the load to a specific lane or speed, or rejecting portions of the proposed route.
Superload engineering analysis is one reason why very large equipment moves — power transformers in the 200,000 to 800,000-pound range, for example — require 2 to 4 weeks of lead time from quote to departure. The analysis cannot be rushed without compromising safety, and the results cannot be predicted before the analysis is complete.
Overhead Clearance Planning
The Vertical Clearance Challenge
For tall loads — cranes in transport configuration, tall industrial equipment, or loads on high-deck trailers — vertical clearance is as important as bridge weight. The height of a load changes when it is placed on a trailer: a machine that stands 12 feet tall sitting on the ground may be 14 to 16 feet off the ground when loaded on a lowboy trailer, depending on the trailer's deck height and whether the load's center of gravity affects how it sits on the trailer.
Measuring the loaded height correctly before routing is essential. A common mistake is using the equipment manufacturer's stated height rather than the measured height in transport configuration with the specific trailer being used. Height varies with tire inflation, trailer loading, and whether any attachments are included. For critical clearance situations, carriers measure the loaded combination before routing rather than relying on estimated heights.
Utility Lines and Non-Bridge Overhead Obstructions
Bridges are catalogued in federal and state databases. Utility lines are not. Power lines crossing roads, telephone cables, fiber optic cables, and cable TV lines are installed by individual utilities and tracked only in utility company records — not in any publicly searchable permit database. When a route passes under a utility line that hangs low enough to pose a clearance risk, the carrier or escort must coordinate with the utility company to have the line temporarily lifted or de-energized for the load's passage.
Utility line lifts are a specialized service performed by utility crews. They require advance notice — typically several days minimum for routine lifts, longer for high-voltage transmission lines — and may carry a cost for the shipper or carrier depending on the utility's policies. Route planning for tall loads must include a review of aerial imagery for the proposed route to identify utility lines that are not in any government database but could present a clearance risk.
Traffic Infrastructure: Signals, Signs, and Gantries
Traffic signals hung on mast arms over roadways are typically at least 17 to 18 feet above the road surface. However, older installations, signal heads hanging from span wire between two poles, and low-mounted gantry signs can present clearances below 16 feet. Urban corridors with dense signal infrastructure are a routine clearance challenge for tall loads. The pilot car's height pole surveys these obstructions before the load moves through, and the carrier coordinates with local traffic management if a signal must be temporarily raised or moved for the load's passage.
Restricted and Controlled Corridors
Interstate Restrictions on Very Wide Loads
The interstate highway system carries most heavy haul moves because it offers the best bridge inventory, the widest pavement, and the fewest overhead obstructions. However, some very wide loads are restricted even on interstate highways. Loads wider than 16 feet may be prohibited from certain interstates that pass through dense urban areas, elevated structures, or tunnels. The permit office identifies these restrictions during route approval and requires the carrier to use alternate surface roads for those segments — often adding time and distance to the move.
Tunnel Restrictions
Tunnels present multiple restrictions for oversize loads. Width restrictions inside the tunnel may be narrower than the open approach roadway. Height restrictions in tunnels are absolute — unlike an open-air road where an overheight load can sometimes pass if the overhead obstruction has a physical clearance margin, a tunnel ceiling is fixed. Weight restrictions may also apply if the tunnel structure has a lower load rating than the approach bridges. Loads that are overheight are generally not permitted through tunnels and must use alternate routes that bypass the tunnel structure entirely.
Urban and Downtown Routing
Urban deliveries — a transformer being moved to a downtown substation, a crane being erected in a city-center construction site — introduce dense routing constraints. Signal timing coordination, police escort through intersections, temporary lane closures, and very early morning or late-night travel windows are commonly required for urban heavy haul moves. The carrier coordinates these logistics with local authorities well in advance, and the move may require a dedicated permit from the city in addition to the state permit for the broader route.
The Permit Routing Process
How State Permit Offices Approve Routes
When a carrier submits a permit application, the permit office reviews the proposed route against its database of bridge ratings, clearances, and restrictions. In states with electronic permit systems — which now includes most major permit-issuing states — this review is partially automated. The system flags structures that may not support the proposed load or that fall below the load's height, and the permit reviewer either approves the route, requires the carrier to modify it, or refers it for engineering analysis if the load falls in the superload category.
Some states issue permits that specify the approved route in detail — down to specific highway numbers, interchange ramps, and turning movements in some cases. The permitted carrier is legally required to follow that route. Deviating from the permitted route, even to take what appears to be an equivalent alternate, is a permit violation. If conditions on the road require a detour, the carrier must stop and contact the permit office before making the change.
Multi-State Permit Coordination
A load moving from Georgia to Texas crosses through Georgia, Alabama, Mississippi, and Louisiana at minimum — four different state permit offices, each with its own routing database, its own staff, and its own timeline. The route approved by Georgia may not match the route preferred by Alabama, and the route approved by both may need to be adjusted to satisfy Mississippi's requirements. R&RM LLC handles all multi-state permit applications through our permit services team, coordinating each state's requirements into a unified route that satisfies all jurisdictions before the load moves.
This coordination is one reason shippers benefit from working with a carrier who handles their own permits rather than outsourcing them. When a carrier manages the permit process directly, they can identify route conflicts between state requirements early and resolve them before the load is ready to depart — rather than discovering on departure day that one state has issued a permit for a different highway than another state requires.
Route Surveys: When a Physical Inspection Is Required
What a Route Survey Involves
A route survey is a physical inspection of the planned route by a qualified driver operating a pilot car equipped with a height pole. The surveyor drives the entire planned route — every mile from origin to destination — measuring overhead clearances, confirming bridge approach conditions, identifying tight turns, checking road surface conditions at critical points, and photographing any potential obstacle. The survey report is submitted to the permit office and may be required as a condition of permit issuance for very wide or very tall loads.
Route surveys take one to three days for typical interstate moves and longer for complex routes with many overhead obstructions, utility coordination requirements, or difficult access points. The cost of the survey is borne by the shipper as part of the overall move cost. For complex moves, the survey is not optional — it is a condition of the permit and a prerequisite to departure.
When Route Surveys Are Required
Most states require route surveys for loads that exceed specified width or height thresholds. Common triggers include loads wider than 16 feet, loads taller than 16 feet, superloads over 150,000 to 200,000 pounds gross weight, and loads moving on non-interstate routes where bridge and clearance data may be less complete. Individual states set their own thresholds; R&RM LLC's permit team knows which states require surveys for which load types and includes survey coordination in the overall move planning timeline.
Common Route Planning Challenges and How They Are Handled
The Load Fits on Paper but the Route Is Blocked
One of the most common surprises in oversize routing is discovering that a load that appears to be straightforward — modestly overwidth, not overweight — cannot use the most direct route because of one specific bridge, one low utility crossing, or one posted road weight restriction. In these cases, the carrier identifies the next-best route and submits it for permit approval. Depending on the state and the nature of the restriction, the alternate route may add 30 miles or 300 miles to the move.
Shippers who are time-sensitive should discuss potential routing constraints at quote time. An experienced carrier can often identify the likely routing issues for a given load on a given corridor before the permit is submitted, flagging constraints that may affect the move timeline or cost. If you are planning a move on a tight deadline, confirming the route is feasible — including the permit timeline for that specific route — before finalizing the schedule is important.
Seasonal Road Closures and Spring Weight Restrictions
Spring weight restriction periods — when state and local road authorities limit weights on roads that are softened by frost thaw — affect oversize routing from roughly February through May depending on the latitude. Roads that are accessible for oversize moves in other seasons may be posted at reduced limits during spring breakup, forcing detours onto alternate highways or delaying the move until restrictions are lifted. Our guide to seasonal heavy haul covers timing strategies to work around spring restrictions.
In-Transit Route Changes
Occasionally, a route that was clear at permit time becomes blocked in transit — a road closure from an accident, a bridge temporarily closed for emergency repairs, a sudden construction closure. When this happens, the driver must stop the load and contact both the carrier's dispatcher and the permit office in the affected state before proceeding onto an unpermitted road. An experienced dispatcher can often reach the permit office and obtain verbal authorization for an alternate segment quickly, allowing the load to resume movement with minimal delay. Without an experienced dispatcher available around the clock, this situation can strand a load for many hours.
How R&RM LLC Plans Every Route
R&RM LLC has been routing oversize and overweight loads across all 48 continental states since 2011. Our dispatch team handles the full route planning process: load dimension verification, multi-state permit submission and coordination, route survey arrangement when required, escort coordination, and in-transit support for drivers. We are reachable by phone at (404) 987-6225 or through our online quote form to start the planning process for your load.
When you provide us with accurate load dimensions and the origin and destination, we build the route before we quote — so the price you receive reflects the actual routing complexity, not an optimistic straight-line estimate that changes when permits are submitted. For oversize load transport and overweight load transport, getting the route right from the start is the difference between a smooth delivery and an expensive delay.
Frequently Asked Questions
Why does a carrier need to plan a specific route instead of just following GPS?
Standard GPS is designed for standard vehicles and has no information about bridge weight ratings, posted low clearances, width-restricted roads, or state permit routing requirements. For oversize loads, every route must be verified against bridge formula limits for every structure on the path, checked for overhead clearances, and approved by each state's permit office. Using standard GPS on a heavy haul move can result in a bridge strike, a stuck truck, a damaged load, and serious legal liability for permit violations.
What is a route survey and when is one required?
A route survey is a physical inspection of the planned route by a pilot car before the load moves. The surveyor drives the route to confirm overhead clearances with a height pole, identify tight turns, check bridge approach conditions, and flag any obstacle that may not be in the permit database. Most states require route surveys for loads exceeding 16 feet in width or height, or for superloads above specified weight thresholds. The survey cost is included in the overall move cost.
Can the shipper request a specific route?
Shippers can express route preferences — particularly if a specific highway better matches the delivery schedule or avoids a known site access issue. However, the final route must satisfy each state's permit requirements and pass bridge formula analysis. If a preferred route cannot be permitted, the carrier explains why and provides the approved alternate. For most straightforward oversize moves, the carrier's proposed route is the most practical option and matches what the shipper would choose anyway.
What happens if the route is blocked or changed after permits are issued?
The driver must stop and contact the carrier's dispatcher and the permit office before deviating from the permitted route. An experienced dispatcher can often secure authorization for a short alternate segment quickly. Moving a permitted oversize load onto a non-permitted road is a permit violation regardless of the reason for the detour. Carriers with 24/7 dispatch — like R&RM LLC — handle these situations without leaving the driver without support on the roadside.