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Table 1 Examples of estimating efficiency indices for selected treatment types

From: The evaluation of safety efficiency of non-urban infrastructure improvements; a case-study

(a) Upgrading a single-carriageway to a dual-carriageway road section
Accident type Efficiency index, 95 % confidence interval Meaning
Injury accidents −34 % [−49 %; −13 %] Reduction
Severe accidents −22 % [−62 %; +63 %] Reduction trend
Total accidents −31 % [−41 %; −19 %] Reduction
Injury accidents, accounting for selection bias −32 % [−48 %; −11 %] Reduction
Severe accidents, accounting for selection bias −17 % [−60 %; +74 %] Reduction trend
(b) Barrier installation - building a rigid median, on a single-carriageway road section
Accident type Efficiency index, CI Meaning
Injury accidents −61 % [−74 %; −42 %] Reduction
Severe accidents −71 % [−89 %; −20 %] Reduction
Total accidents −23 % [−40 %; −2 %] Reduction
Injury accidents, accounting for selection bias −50 % [−68 %; −24 %] Reduction
Severe accidents, accounting for selection bias −49 % [−83 %; +53 %] Reduction trend
(c) Resurfacing and replacing lenses by LEDs, at a signalized junction
Accident type Efficiency index, CI Meaning
Injury accidents +8 % [−32 %; +72 %] Increasing trend
Severe accidents +17 % [−86 %; +868 %] -- a
Total accidents +7 % [−22 %; +46 %] Increasing trend
  1. a No result (insufficient data)