  Vulnerable road users (VRUs) such as pedestrians, cyclists and motorcyclists
are at the highest risk in the road traffic environment. Globally, over half of
road traffic deaths are vulnerable road users. Although substantial efforts are
being made to improve VRU safety from engineering solutions to law enforcement,
the death toll of VRUs' continues to rise. The emerging technology, Cooperative
Intelligent Transportation System (C-ITS), has the proven potential to enhance
road safety by enabling wireless communication to exchange information among
road users. Such exchanged information is utilized for creating situational
awareness and detecting any potential collisions in advance to take necessary
measures to avoid any possible road casualties. The current state-of-the-art
solutions of C-ITS for VRU safety, however, are limited to unidirectional
communication where VRUs are only responsible for alerting their presence to
drivers with the intention of avoiding collisions. This one-way interaction is
substantially limiting the enormous potential of C-ITS which otherwise can be
employed to devise a more effective solution for the VRU safety where VRU can
be equipped with bidirectional communication with full C-ITS functionalities.
To address such problems and to explore better C-ITS solution suggestions for
VRU, this paper reviewed and evaluated the current technologies and safety
methods proposed for VRU safety over the period 2007-2020. Later, it presents
the design considerations for a cellular-based Vehicle-to-VRU (V2VRU)
communication system along with potential challenges of a cellular-based
approach to provide necessary recommendations.
