Model Description Specification I Single linear term Logit(P)= α + β1AGE + β2ISS + β3GCS + β4RR + β5SBP IIa Dummy variables on 5 categories Logit(P)= α + β1AGE55-64 + β2AGE65-74 + β3AGE75-84 + β4AGE>84 + β5ISS9-15 + β6ISS16-24 + β7ISS25-40 + β8ISS>40 + β9GCS9-12 + β10GCS6-8 + β11GCS4-5 + β12GCS3 + β13RR0+ β14RR1-5 + β15RR6-9 + β16RR>29 + β17SBP0+ β18SBP 1-49 + β19SBP 50-75 + β20SBP 76-89 IIb Dummy variables on 4 categories Logit(P)= α + β1AGE65-74 + β3AGE75-84 + β4AGE>84 + β5ISS9-15 + β6ISS16-24 + β8ISS>24 + β9GCS9-12 + β10GCS6-8 + β11GCS3-5 + β13RR0-5+ β15RR6-9 + β16RR>29 + β17SBP0-49+ β19SBP 50-75 + β20SBP 76-89 IIc Dummy variables on 3 categories Logit(P)= α + β2AGE65-74 + β4AGE>74 + β5ISS9-15 + β8ISS>15 + β9GCS9-12 + β12GCS3-8 + β13RR0-9+ β16RR>29 + β17SBP0-75+ β20SBP 76-89 IId Dummy variable on 2 categories Logit(P)= α + β4AGE>65 + β5ISS>15 + β9GCS>8 + β13RR0-9/>29+ β17SBP0-89 III FP Logit(P)= α + β1AGE3+ β2(AGE3 X log(AGE))I + β3ISS-1+ β4log(ISS)I + β5log(GCS) + β6GCS3 + β7log(RR)+ β8(log(RR) X log(RR))I + β9SBP+ β10log(SBP)I IV GAM Logit(P)= α + s(AGE)+ s(ISS)+ s(GCS)+ s(RR)+ s(SBP) Logit(P) is the log odds of the probability of hospital mortality, ISS: Injury Severity Score; GCS: Glasgow Coma Score; RR: Respiratory Rate; SBP: Systolic Blood Pressure, FP: Fractional Polynomials, GAM: Generalized Additive Model, S: cubic smoothing spline

Table 1: Models used for analyses.