Bridge Copilot is a web-based bridge planning tool that automates the preliminary design computations in a Type, Size, and Location (TS&L) study. It generates multiple structural alternatives, selects girder sizes, estimates construction costs, and runs Monte Carlo risk analysis — from a handful of project inputs. A type study that takes a senior engineer one to two days to produce manually takes Bridge Copilot under five minutes.
This page explains the engineering workflow behind the tool, what computations it performs, and where it fits in a typical bridge project delivery process.
Early in a bridge project, owners and engineers must answer a set of questions before committing to final design:
Answering these questions traditionally requires manual calculations, spreadsheet models, and engineering judgment built up over years of practice. Bridge Copilot encodes that judgment into a deterministic rules engine aligned with AASHTO LRFD, allowing less experienced engineers to produce defensible preliminary designs and allowing senior engineers to evaluate more alternatives in less time.
Step 1 — Project Input. Enter: bridge location (latitude/longitude), total crossing length in feet, number of traffic lanes, and design speed. These four inputs drive every downstream calculation.
Step 2 — Seismic Hazard Retrieval. Bridge Copilot queries USGS hazard data for the project coordinates and returns site-specific Peak Ground Acceleration (PGA), 0.2-second spectral acceleration (Ss), and 1.0-second spectral acceleration (S1) consistent with AASHTO LRFD seismic design requirements. These values identify whether seismic isolation or special detailing may be required.
Step 3 — Alternative Generation. The engine applies AASHTO LRFD span-to-depth heuristics, regional span norms, and constructability rules to generate three preliminary bridge concepts. Alternatives typically differ in girder material (precast prestressed concrete vs. steel plate girder), span count, span arrangement, and substructure type. Each alternative is fully defined — span lengths, deck width, girder count, approximate girder depth — without further input from the engineer.
Step 4 — Girder Optimization. For precast concrete alternatives, the tool selects from a library of standard wide-flange girder sections (WF36TDG through WF95TDG) using span-to-depth ratio limits and practical girder spacing constraints (typically 6 ft to 12 ft on-center). The output identifies the controlling section, estimated strand count, and girder spacing satisfying AASHTO LRFD requirements.
Step 5 — Cost Estimation. Construction cost is computed by component: superstructure (girders, deck, diaphragms), substructure (piers, abutments, foundations), approach slabs, traffic barriers, drainage, and mobilization. Unit costs are sourced from regional bid history data and adjusted by state location factor. The result is an itemized estimate in current dollars.
Step 6 — Monte Carlo Risk Analysis. Bridge Copilot runs 10,000 simulation iterations applying probability distributions to the key cost drivers (unit price variability, quantity uncertainty, contingency factors). The output is a cost probability distribution with P10, P50, and P90 values. P10 means there is a 10% probability the project costs less than that figure; P90 means a 90% probability it costs less. This format is standard for FHWA risk-based cost estimation and capital programming submissions.
Step 7 — Comparison, Critique, and Export. All alternatives are displayed in a side-by-side comparison table and a real-time 3D model. The critique module checks each design against AASHTO LRFD requirements and returns a scored list of findings. Engineers can then export to PDF (formatted type study summary), Excel (cost backup workbook), DXF (plan and elevation geometry for CAD), or IFC (BIM-compatible geometry).
| Bridge Copilot is... | Bridge Copilot is not... |
|---|---|
| A TS&L / type study automation tool | A final design or load-rating tool |
| An alternatives screening and comparison tool | A replacement for AASHTOWare, CSiBridge, or LARSA |
| An order-of-magnitude cost estimator (±20–30%) | An engineer's stamp or design certification |
| An AASHTO LRFD-aligned preliminary rules engine | A seismic or wind detailed analysis tool |
| A tool for consultants, DOTs, and project managers | A replacement for structural engineering judgment |
| Bridge Type | Typical Span Range | Sections / Notes |
|---|---|---|
| Precast prestressed concrete wide-flange girder | 40–175 ft per span | WF36TDG – WF95TDG |
| Steel plate girder | 80–250 ft per span | Custom plate sizing |
| Multi-span continuous (precast or steel) | Up to 5 spans | Intermediate pier optimization included |
In-house DOT engineers use Bridge Copilot to prepare or check type study documents before committing to consultant procurement. Having a rapid independent estimate provides leverage in scoping consultant contracts and verifying that proposed alternatives are reasonable before approving scope.
Bridge design consultants use Bridge Copilot during proposal preparation to quickly produce preliminary cost estimates and identify constructability risks before a project is awarded. The tool also supports QC of junior engineers' type study work — a senior engineer can regenerate the analysis in minutes and compare results against the submitted package.
Program-level decision-makers use the Monte Carlo output for capital programming submissions. The P10–P50–P90 cost range provides the risk-based estimate format increasingly required by FHWA for major bridge projects. A single-point estimate no longer satisfies most risk-informed planning processes; Bridge Copilot produces the range by default.
Bridge Copilot produces Class D preliminary cost estimates consistent with AASHTO guide specifications for cost estimating. Expected accuracy is ±20–30% of final bid price at the time of estimate. Cost estimates do not include right-of-way, utility relocation, environmental mitigation, or construction management fees.
Bridge Copilot is a web-based SaaS application requiring no software installation. The backend engineering engine is built in Python and implements AASHTO LRFD rules deterministically — it does not use a large language model to make structural decisions. AI components are limited to design critique summarization and conversational assistance. All structural computations are rules-based and auditable.
The tool runs in any modern web browser. No download, no license server, no VPN. Project data is stored securely in a cloud database with per-user access controls.
No. Bridge Copilot automates the computational work in preliminary design but does not exercise professional engineering judgment. The engineer decides whether the generated alternatives are appropriate for the site, reviews the output critically, and stamps the final deliverable. The tool is intended to expand what one engineer can accomplish in a given time — not to eliminate engineering from the process.
Most engineers doing TS&L studies use a combination of personal spreadsheets, published span tables, and experience-based judgment. Bridge Copilot automates the same process with consistent rules, eliminates transcription errors, adds real-time 3D visualization, integrates seismic data retrieval, and outputs a formatted document — all in the same time it takes to set up a spreadsheet template.
Bridge Copilot applies regional cost adjustments by state and AASHTO LRFD as the base design standard. It does not currently implement state-specific design manuals (e.g., WSDOT, Caltrans, TxDOT supplements). Engineers should review output against their specific agency's standard details and specifications before submitting a type study.
The free trial includes access to the full design engine, three bridge project slots, and PDF/Excel export. The interactive sandbox at bridgecopilot.com/sandbox is always free and requires no account.
Bridge Copilot is free to try. No credit card required. The sandbox lets you run a complete bridge alternatives analysis on a sample project without signing up.
© 2026 Bridge Copilot LLC — Home · Pricing · Documentation · Privacy Policy · Terms of Service