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Spec’ Writing


Vocational vehicle specifications serve as building blocks for a fleet and provide financial responsibility for the end product. As work trucks become more complex, mistakes are inevitable. A well-written specification can be valuable when determining who is responsible for correcting errors and monetarily accountable.

Efficient specifications can lower an organization’s overall acquisition and lifecycle costs. They help eliminate guesswork, enabling companies to provide customers with the envisioned end product. Poorly done specifications often result in time-consuming, expensive rework. Avoiding this can allow vendors to reduce financial liability when responding to purchase solicitations—in turn, potentially leading to cost reductions.

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Effective communication is critical to ensuring well-written specifications and providing the best value for capital spent. There are several types of spec’s, and understanding key differences between them can be critical when it comes to final product and price.
Generic specifications are written to allow multiple vendors and suppliers to comply without making unreasonable changes to their standard products. This can be a useful format for truck equipment when used in competitive bid situations.

Proprietary specifications incorporate features specific to a certain make or model and are written around a specific unit, excluding all others. Advantages to using this type of spec’ include obtaining a product only available from a sole source or if the spec’ is written around the idea of standardization and can include multiple vendors. It’s important to use valid selection criteria—proprietary spec’s are not effective when used to incorporate features for a specific make or model to give advantages to potential vendors during a competitive bid process.

Predatory specifications are written to artificially disqualify a single vendor or make them take unacceptable exceptions to specifications. These are not considered an effective practice and should be avoided.

Four common types of specifications can be written:

  • Engineered
  • Functional
  • Performance
  • Hybrid

Engineered spec’s include the most detail and require a high level of engineering expertise. The writer assumes a significant amount of liability for the final product, but has complete control over it. In most cases, these are used for extremely specialized, customized offerings and often result in the most expensive end product with long production times.

Functional specifications describe intended equipment usage, but provide minimal guidance for actual design. While easy to write, these spec’s rely on vendors to interpret requirements and final product applications. This leaves little control over design and makes it difficult to standardize components on a global level.

Performance specifications are similar to functional, but incorporate specific requirements for the completed unit (e.g., crane lifting capacity or maximum operating vehicle speed). They are easy to write and provide vendors with significant flexibility; however, there is less control over final design and standardization.

Hybrid or composite spec’s combine the best features of engineered, functional, and performance. The writer can fully define all requirements, as well as incorporate standard components without being excessively restrictive to vendors.


Some fleet managers stick with what worked previously and won’t go beyond manufacturer changes from model year to model year. While this might sound like a concrete idea, it can become a slippery slope and result in outdated and inefficient operations.

Take a step back and consider your current equipment functionality. Is the equipment that’s being replaced the most efficient for the task? Have job requirements shifted over time? Change can bring opportunities to increase efficiency, so it’s important to overcome the mindset of replacing equipment with comparable items.


Several steps are necessary for writing effective specifications—starting with defining the application. Don’t make decisions based on what everyone else is doing or assume past needs equal current. Look at operating environment and drive and duty-cycles, and identify valid functional requirements, such as payload and dimensional considerations. Define performance conditions like road speed and gradability, and outline design constraints, such as operating environments, overall weight, vehicle dimensions, and other regulatory barriers.

It is critical to design second units, such as body and auxiliary equipment, before the chassis. Avoid the pitfall of buying a chassis and making it work. Once all of the details are finalized, design the chassis and write the specification.


Fleet managers are often expected to be subject matter experts in various areas. With constant changes in available alternatives and regulatory requirements, taking advantage of resources will help optimize equipment and chassis designs. Truck equipment manufacturers, distributors, upfitters, and OEM representatives can be excellent sources when designing and spec’ing.
NTEA offers data and resources to help fleet managers optimize their operations and benchmark with others in the vocational community. Visit for articles, training offerings, regulatory information, and more.


Christopher Lyon is the director of fleet relations for NTEA. Established in 1964, NTEA represents more than 1,950 companies that manufacture, distribute, install, sell, and repair commercial trucks, truck bodies, truck equipment, trailers, and accessories. Buyers of work trucks and the major commercial truck chassis manufacturers also belong to the Association. NTEA provides in-depth technical information, education, and member programs and services, and produces The Work Truck Show®.


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