An expert inspection of road conditions before the road accident on Struma motorway occured, conducted by an international auditor, has established that the assembly of the roadside safety crash barriers does not meet requirements.

Moreover, a multitude of road accidents have occurred in the road section where the bus accident took place, damaging the crash barriers. This led to their being reinstalled in the median strip but their assembly was faulty. This is the reason why the crash barrier, which is supposed to withstand the weight of a 2-ton vehicle, was broken despite the low speed of the bus when it hit it. The probe also established there are missing road signs and damaged road surface marking. The audit was commissioned by the Road Safety Institute.