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Table 2 Summary of evaluation results for treatments on road sections: efficiency indices and their 95 % confidence intervals

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

Type of infrastructure improvement (#) Injury accidents Severe accidents Total accidents
Upgrading a single-carriageway to a dual-carriageway road section (2) −32 % [−48 %; −11 %] Reduction trend, ns −31 % [−41 %; −19 %]
Building a median on a road section crossing an urban area (2) No change -- −53 % [−66 %; −37 %]
Barrier installation - building a rigid median, on a single-carriageway road (4) −50 % [−68 %; −24 %] Reduction trend, ns −23 % [−40 %; −2 %]
A combined treatment: barriers, road marking/signing, on a single-carriageway road (4) Increasing trend, ns -- −13 % [−27 %; +3 %]*
A combined treatment: barriers, road marking/signing, on a dual-carriageway road (3) No change No change −14 % [−22 %; −6 %]
A combined treatment: resurfacing, road marking, barriers' treatment, on a single-carriageway road (6) −16 % [−29 %; −1 %] No change −20 % [−28 %; −11 %]
A combined treatment: resurfacing, road marking, barriers' treatment, on a dual-carriageway road (6) −23 % [−30 %; −16 %] No change No change
A combined treatment: barriers, resurfacing, shoulders, on a single-carriageway road (5) −12 % [−23 %; −0 %] Increasing trend, ns −19 % [−25 %; −13 %]
A combined treatment: signs, pavement, shoulders, on a single-carriageway road (1) Reduction trend, ns Reduction trend, ns Reduction trend, ns
A combined treatment: resurfacing, crash cushions' installation, barriers' treatment, on a dual-carriageway road (1) No change No change −17 % [−24 %; −11 %]
Pavement treatments, including road marking, raised markers, on a single-carriageway road (1) No change Reduction trend, ns −23 % [−38 %; −5 %]
  1. Notes to Table 2: # number of sites treated; 35 road sections in total. The numerical results presented are significant at 0.05 confidence level; * significant at 0.1 level; ns - not significant
  2. "--" means no result (insufficient data); "no change" indicates that average value of the efficiency index is below 5 %