Table 1

Values used in the Markov model evaluating NSZs relative to the no intervention

Parameter	Base	SE/range	Distribution	Source
Cost (2016 US$)
Cost of injury (per case)
Lifetime medical cost due to non-fatal traffic injury	3608	902	Gamma	CDC²⁶
Lifetime medical cost due to fatal traffic injury	16 265	4066	Gamma	CDC²⁶
Lifetime productivity cost due to non-fatal traffic injury	6682	1671	Gamma	CDC²⁶)
Lifetime productivity cost due to fatal traffic injury	1 277 926	319 482	Gamma	CDC²⁶
Intervention cost (per person)
Proposed speed bumps	1.30	0.32	Gamma	Bushell et al ²⁴
Existing speed bumps	0.35	0.09	Gamma	Bushell et al ²⁴
Gateways	0.60	0.15	Gamma	Bushell et al ²⁴
20 mph markings	0.28	0.07	Gamma	Bushell et al ²⁴
Health utility decrement
Serious traffic injury	0.45	Low: 0.36; high: 0.53	Triangular	EQ5D survey
Probability
% Case fatality ratio of traffic injury	0.38	0.02	Beta	NYS Department of Motor Vehicles²¹
% Serious injury among non-fatal injuries	7.54	0.13	Beta	NYS Department of Motor Vehicles²¹
% Background traffic injury probability	0.15	0.01	Beta	NYC Department of Transportation¹⁷, NYS Department of Motor Vehicles²¹
% Traffic injury reduction in the NSZs	8.74	Low: 1.02; high: 16.47	Triangular
% Potential injury increase in control neighbourhoods	0.31	Low: −3.64; high: 4.27	Triangular
Other
Baseline age	36			NYC Department of City Planning¹⁵
Time horizon	54
% Discount rate	3%	Low: 0%; high: 5%	Triangular	Paulden et al 16
Frequency of NSZs reconstruction (every n years)	5	Low: 3; high: 7	Triangular
Population in NSZs	518 420			NYC Department of City Planning¹⁸

EQ5D, EuroQol Five Dimensions Questionnaire; NSZ, neighbourhood slow zone; NYC, New York City; NYS, New York State SE, standard error