Global Navigation Satellite System (GNSS) is now widely used in transportation

and the users have shown growing concerns with the service reliability of GNSS. However

due to the factors such as ionospheric scintillation

multi-path effect

and electromagnetic interference

GNSS has inherent vulnerability

which may damage the quality of GNSS service

and even cause enormous risks. Assessing GNSS vulnerability and releasing alarms to users when vulnerability factors happen are the valid way to consolidate GNSS utilization. To assess GNSS vulnerability under urban roads

this paper proposes three proper vulnerability assessment indexes and conducts vulnerability assessment by the utilization of entropy weight method. Road experiments showed that tunnel

urban canyon

avenue and open road are decreasingly vulnerable

and the algorithm proposed is capable of assessing GNSS vulnerability of urban roads.