With the continuous development of modern railway transport, the demands and requirements of wireless communication networks for railways are continuously changing and increasing. Insufficient coverage is one of the key challenges in the deployment and maintenance of mobile cellular networks, therefore accessible and precise methods of investigating radio coverage conditions should be determined and described. The paper presents the results of testing the radio coverage of 2G, 3G and 4G service areas of cellular mobile network operators along the railway. The experimental studies were conducted on the Riga–Jelgava railway line of the Latvian Railway company (LDz) using mobile terminals with the installed cellular mobile communication network testing and parameter monitoring software. Results of experimental measurements were used to determine network coverage areas and the influence of the environment on the uniformity of radio coverage. Areas with the large attenuation of radio signals were marked on the provided coverage maps, measures for improving the quality of mobile communications for railway applications were observed as well.