Trains on JR Nara Line used to take a long travel time because they have to wait for two trains' passing each other on single track section.
Then, JR West and Kyoto Prefecture Government has planned to extend double track section. While Kyoto Prefecture Government has aimed at full double track of JR Nara Line, JR West has aimed at double track only a part of JR Nara Line in terms of cost-effective managing. As a result, the following section was determined to construct double track
JR Fujinomori〜Uji
Shinden〜Joyo
Yamashiro-Taga〜Tamamizu
After completion of the construction, JR Nara Line between Kyoto and Joyo will be full double track section. The reason why the section between Yamashiro-Taga and Tamamizu was also added to the plan despite that the section is not included between Kyoto and Uji is to leave the possibility to begin construction of full double track between Joyo and Kizu.
I summarized an ariticle of http://www.kyoto-np.co.jp/top/article/20120125000030 (Kyoto Newspaper)
