  As the traffic safety has become of utmost importance, much attention is
given to intelligent transportation systems (ITSs), and more particularly to
vehicular communications (VCs). Moreover, 50 % of all crashes happen at road
intersections, which makes theme a critical areas. In this paper, we
investigate the improvement when implementing maximum ratio combining (MRC) in
cooperative VCs transmission schemes using non-orthogonal multiple access
scheme (NOMA) at road intersections. We consider that a source transmits a
message to two destinations with a aid of a relay. The transmission undergoes
interference generated from a set of vehicles on the roads. We obtained closed
form outage probability expressions, and we extend the derivation for a
scenario involving K destination nodes and several road lanes. The performance
of MRC cooperative NOMA is compared with the standard cooperative NOMA, and we
show that implementing MRC with NOMA offers a significant improvement over the
standard cooperative NOMA. Also, we compare the performance of MRC using NOMA
with MRC cooperative orthogonal multiple access (OMA), and demonstrate that
NOMA significantly outperforms OMA. We conclude that it is always beneficial to
use MRC and NOMA even at the cost of implementation complexity. Finally, we
demonstrate that the outage probability increases drasticallyen the vehicles
are closer to the road intersection, and that using MRC with NOMA improves
significantly the performance in this context. To verify the correctness of our
analysis, extensive Monte-Carlo simulations are carried out.
