The solicitation does not have a single desired temperature range for Phase I. Offerors should propose defensible temperature thresholds tied to the intended packaging type, commodity hazard, and failure mode. The key requirement of the proposed solution is a visible, distinct, and durable color change that provides operators and first responders a meaningful warning of increasing internal thermal stress before packaging failure.

Plastic or glass may be used as substrates for coating formulation development or color-change testing. However, offerors should also demonstrate adhesion and compatibility with transportation-relevant packaging materials such as steel, aluminum, or composite materials.

The solicitation does not define a number of cycles, but offerors should define and justify the number of cycles or replicate tests needed to demonstrate repeatability that the proposed solution works.

1. What is DoT's desirable temperature range to show the color change?
2. Can plastic (or glass) be considered common substrate material for Phase-I?
3. How many cycles are expected to prove the "repeatability" of color change?

The solicitation does not require the coating to physically measure the internal temperature, but it should require the technology to be risk-relevant. That means the indicator must correspond to temperature thresholds that matter for package safety, including internal temperature rise, pressure increase, thermal runaway risk, venting, or loss-of-containment conditions. External surface indication alone should not be considered sufficient unless the proposer validates the correlation to internal package risk.