Transportation Management System (TMS): Functions and When to Buy

What a TMS is

A transportation management system (TMS) is software that plans, books, tracks and pays for freight. It covers everything outside the warehouse walls: choosing the carrier, building the load, routing, tracking the delivery and checking the freight invoice.

A warehouse management system runs what happens inside the warehouse, an MES runs the shop floor, and the ERP holds orders, invoices and accounting. The TMS sits between the shipped order and the customer who receives it.

TMS visual map

The map shows the freight cycle (quote, route, track and audit), the dimensional weight example and the monthly KPIs.

Core TMS functions

• Rating and carrier selection: compares each carrier's rates, transit time and service level for every order and applies rules, such as lowest cost within the required lead time.
• Load consolidation and planning: groups orders by destination and vehicle, respecting weight, volume and delivery window.
• Route planning: sets the stop sequence. The underlying logic is in vehicle routing and the traveling salesman problem; the system applies it with maps, constraints and the real fleet.
• Dock and pickup scheduling: books the loading window and keeps trucks from queuing in the yard.
• Tracking and exceptions: receives carrier status (picked up, in transit, delivered, damaged, refused) and raises an alert before the customer complains.
• Freight audit and payment: compares the quoted freight with the invoiced amount and blocks payment of discrepancies.
• Reporting: cost per kg, freight as a share of sales, on-time delivery and invoice discrepancy rate.

Example: a quote with dimensional weight

A plant ships 4,000 kg of cargo that occupies 18 m³, with an invoice value of $120,000. The customer requires delivery within 3 days. Carriers charge on the higher of actual weight and dimensional weight. In this example, all of them use a factor of 300 kg/m³.

Dimensional weight = volume (m³) × factor (kg/m³) = 18 × 300 = 5,400 kg

Because 5,400 kg is greater than 4,000 kg, freight is charged on 5,400 kg.

The cheapest carrier (C) misses the deadline. Of the two that meet it, the TMS picks B at $1,620, which is $270 less than A. Per actual kilogram, B costs $1,620 ÷ 4,000 = $0.405/kg.

On the invoice, carrier B billed $1,780. The discrepancy is $1,780 − $1,620 = $160, or 9.9% above the quote. Without automatic audit, this kind of overcharge is usually paid without anyone noticing.

Transportation KPIs

With TMS data, the month-end review looks like this (example values):

Cost per kg alone is misleading: it rises when the cargo is light and bulky. Track it together with vehicle fill and on-time delivery. For the service-level logic, see service level and fill rate.

When to implement a TMS

A good sign is when the team spends the day quoting and chasing carriers instead of planning. Freight is often one of the largest logistics costs, and the return from auditing invoices and picking the right carrier shows up quickly. Compare the investment against the total cost of ownership: license, integration, training and support.

Implementation steps

1. Map the current process from invoice to delivery and freight payment. A simple process flowchart is enough.
2. Clean the master data: addresses, postal codes, product weights and dimensions. Without correct weight and volume, dimensional weight comes out wrong.
3. Load each carrier's rate tables, with transit rules, surcharges and the dimensional factor.
4. Integrate with the ERP and WMS: orders and invoices enter the TMS without re-keying; status flows back to the ERP.
5. Start with one lane or one carrier and compare planned and actual freight for 30 days.
6. Set the decision rules (lowest cost within lead time, priority for critical customers) and who approves exceptions.
7. Review the KPIs in a weekly meeting and adjust rates and rules.

Common mistakes

• Wrong weight and dimension master data, which produces wrong quotes and wrong audits.
• Choosing only on lowest freight and ignoring transit time, damage and claims.
• Not integrating with the ERP and WMS, which keeps double entry alive.
• Going live without deciding who handles exceptions and invoice disputes.
• Tracking cost per kg only, with no on-time delivery and no vehicle fill.

Frequently asked questions

What does TMS stand for?

Transportation management system. It plans, books, tracks and audits freight.

What is the difference between a TMS and a WMS?

A WMS manages the warehouse (receiving, inventory, picking). A TMS manages transportation after the order leaves shipping.

What is dimensional weight?

It is the weight equivalent of the cargo's volume: volume in m³ times a factor in kg/m³. The carrier bills the higher of actual and dimensional weight.

How do you calculate dimensional weight for 18 m³ at a factor of 300?

18 × 300 = 5,400 kg. If the actual weight is 4,000 kg, freight is charged on 5,400 kg.

Does a TMS replace the ERP?

No. The ERP holds orders, invoices and accounting; the TMS handles transportation decisions and follow-up and integrates with the ERP.

Is a TMS worth it for a small company?

It depends on shipment volume and freight spend. With few shipments and one carrier, a spreadsheet and the carrier's portal are usually enough.

About the author

Vagner Soares

Lean Manufacturing & Behavioral Management Specialist

Over 20 years in the automotive and metalworking industries (GM and Dana), Lean Manufacturing practitioner since 2006. SENAI instructor and mentor in Brazil’s Brasil Mais Produtivo program, delivering consulting, training and audits for 50+ companies, combining quality, productivity and people development.

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