3. Regulatory and consumer test landscapes

Injury limit evaluation only becomes meaningful once you anchor it to a specific test protocol. The same physical quantity — say, a chest acceleration of 55 g — can be a pass in one regime and a fail in another, because each program defines its own channels, filtering, duration windows, and threshold values. Before building any Excel pass/fail engine, you must know which regime you are evaluating against and how that regime defines its injury criteria. This chapter maps the five most relevant landscapes for a global vehicle program: the U.S. FMVSS regulations, the UN ECE regulations, and the three major consumer programs — C-NCAP, Euro NCAP, and IIHS.

Regulation versus consumer rating: two different contracts

FMVSS and ECE are regulations: pass/fail, legally binding for market access, with thresholds set as minimum acceptable protection. Consumer programs (C-NCAP, Euro NCAP, IIHS) are ratings: they publish star scores or category grades, and their thresholds are typically stricter than regulation because they are designed to differentiate vehicles. A vehicle that just passes FMVSS 208 may score poorly in Euro NCAP frontal offset. For an Excel automation project, this distinction matters because regulatory evaluation is a binary gate, while consumer evaluation usually requires scoring logic — points, capping, and weighted aggregation — on top of the raw pass/fail checks.

FMVSS: channel-based, regulation-driven

FMVSS 208 (occupant crash protection) is the reference for U.S. frontal and side evaluation. Its injury criteria are defined on specific channels measured at specific dummy locations. The commonly automated set includes:

• HIC36 — Head Injury Criterion over a 36 ms window, computed from the resultant head acceleration; the regulatory limit is 700 for the driver and 700 for the passenger in the belted frontal test.
• Chest deflection — measured in millimeters at the dummy's chest; the limit depends on dummy type (Hybrid III 50th male versus 5th female).
• Femur axial force — typically limited to 10 kN per leg in the frontal barrier test.
• Neck injury criteria (Nij) — tension, compression, and bending moments combined.

FMVSS 208 also defines the unbelted test at 25 mph into a rigid barrier and the belted test at 30 mph, plus offset and angled barrier variants. The key automation point: FMVSS channels are named consistently in the test data (e.g., HEAD_ACC_RES, CHEST_DEFL), so a lookup table keyed on channel name plus dummy position is the natural Excel structure.

ECE: regulation with its own filter and window conventions

UN ECE R94 (frontal impact) and R95 (side impact) define injury criteria that look similar to FMVSS but differ in detail. HIC is computed over a 36 ms window in R94, but the acceleration signal must be filtered per the regulation's specified channel frequency class (CFC), typically CFC 1000 for head acceleration. Chest deflection limits and the treatment of the 5th percentile female dummy differ from FMVSS. ECE also uses the viscous criterion (VC) for chest in some configurations, which is a velocity-of-deformation measure rather than a pure deflection limit. If your Excel engine hard-codes FMVSS thresholds and channel names, it will silently mis-evaluate an ECE dataset. The correct design is a regime-keyed threshold table, not a single global constant set.

Consumer programs: stricter thresholds and scoring layers

C-NCAP (China) follows a structure close to Euro NCAP but with its own point allocations and threshold values. Frontal 50 km/h full-width and 64 km/h offset tests, side MDB, and whiplash tests each carry points; HIC, chest, and femur limits are set tighter than ECE. C-NCAP also applies capping rules — exceeding a threshold zeroes the sub-item rather than producing a negative score.

Euro NCAP is the most granular. Frontal offset (50 km/h, 40% overlap, deformable barrier), side barrier, side pole, and whiplash are scored separately, and each body region has its own limit curve. Euro NCAP uses limit values and high-performance limits: a result between them earns partial points, above the limit earns zero. This two-tier structure is the single most important difference from regulation and must be modeled explicitly in Excel — a simple "pass if below X" formula is insufficient.

IIHS (U.S. Insurance Institute for Highway Safety) uses its own rating scale (Good / Acceptable / Marginal / Poor) and its own test set: moderate overlap frontal, small overlap frontal, side, roof strength, and head restraints. IIHS injury measures are reported per body region with rating boundaries rather than a single pass/fail number. The small overlap test in particular produces different loading paths and different channel behavior than FMVSS 208, so the same dummy channel may need a different threshold and a different evaluation window.

How the regimes differ in practice

The table below summarizes the practical differences that drive Excel design decisions. Values are representative and should be verified against the current published protocol revision before use in production.

Building the regime-aware threshold table

The practical takeaway for the Excel engine is a three-level key: regime → test configuration → body region/channel. Each leaf holds the threshold value, the comparison direction, the filter class, and the evaluation window. A minimal structure looks like this:

Regime      Test              Channel        Limit    Dir   Filter   Window
FMVSS208    Frontal_30mph     HEAD_ACC_RES   700      <=    CFC1000  36ms
ECE_R94     Frontal_64kph     HEAD_ACC_RES   1000     <=    CFC1000  36ms
EuroNCAP    Frontal_Offset    HEAD_ACC_RES   650      <=    CFC1000  36ms
EuroNCAP    Frontal_Offset    HEAD_ACC_RES   500      <=    CFC1000  36ms  (high-perf)
C-NCAP      Frontal_64kph     CHEST_DEFL     50       <=    CFC180   -
IIHS        SmallOverlap      HEAD_ACC_RES   rating   -     CFC1000  36ms

With this table, the pass/fail formula becomes a lookup rather than a hard-coded constant, and adding a new regime is a data change, not a code change. The next chapter builds the HIC and deflection calculations that feed these comparisons; here the goal is to fix the mapping so that every subsequent calculation is evaluated against the correct contract.

The diagram makes the central design rule explicit: the evaluation rule is a property of the full path, not of the channel. A single HEAD_ACC_RES column in the raw data feeds five different rules depending on which regime and configuration the test belongs to. Once this mapping is fixed in a lookup table, the Excel engine can evaluate any dataset against any regime without rewriting formulas — and the pass/fail output remains traceable back to the exact published threshold it was compared against.