We investigate the analytical expressions of typical performance metrics, namely message reception probability, message reception interval, and information dissemination rate, for vehicle-to-everything (V2X) safety communication in urban scenarios. Each of the performance metrics can be expressed in a simple closed form under some moderate assumptions such as vehicles being positioned according to a Poisson process in a two-dimensional plane. Based on the obtained expressions, we analyze the dependence of these performance metrics on the message transmission interval, which is a typical parameter of congestion control of V2X communication. The results show that the optimal message transmission interval that minimizes the average message reception interval can be derived in a simple closed form. The information dissemination rate is insensitive to the message transmission interval.