Luminosity vs. decline-rate relation populated with a subset of CSP-I SNe Ia (Burns et al. 2014) and a few fast decliners from the literature. The relation is parameterised by Δm₁₅ (left) and s_BV (right). The absolute B-band magnitudes are extinction corrected as described by Burns et al. (2014), and distances are computed using a Hubble constant H₀ = 73 km s⁻¹ Mpc⁻¹. A distance modulus of μ = 31.27 mag is used to place SN 2007on (black square) and SN 2011iv (red circle) on the luminosity scale. The blue circles correspond to SNe Ia classified as CL (cool) on the Branch et al. (2006) diagram, whereas the grey circles represent SNe Ia with either different (i.e. SS, CN, BL) or unknown Branch spectral subtype classifications. Additionally, included for comparison are the low-luminosity Type Ia SNe 1986G (yellow diamond) and 1991bg (yellow star), the transitional Type Ia iPTF13ebh (green triangle), and the normal Type Ia SN 2004eo (pink downward triangle). The dashed curves represent the parameterised luminosity vs. decline-rate relation for normal SNe Ia (Phillips et al. 1999) and for the subluminous SNe Ia (Taubenberger et al. 2008). The dotted curve represents an interpolation of the Phillips et al. (1999) relation for SNe Ia with 1.7 < Δm₁₅(B) < 2.0 mag.