more efficient sodium vapor lamps. This triggered an outcry from astronomers at Palomar Observatory north of the city, concerned that the new lamps would increase light pollution and hinder astronomical observation. The city altered its lighting regulations to limit light pollution within of Palomar. In 2011, the city announced plans to upgrade 80% of its street lighting to new energy-efficient lights that use induction technology, a modified form of fluorescent lamp producing a broader spectrum than sodium vapor lamps. The new system is predicted to save $2.2 million per year in energy and maintenance. The city stated the changes would "make our neighborhoods safer." They also increase light pollution. In 2014, San Diego announced plans to become the first U.S. city to install cyber-controlled street lighting, using an "intelligent" lighting system to control 3,000 LED street lights. Transportation With the automobile being the primary means of transportation for over 80 percent of residents, San Diego is served by a network of freeways and highways. This includes Interstate 5, which runs south to Tijuana and north to Los Angeles; Interstate 8, which runs east to Imperial County and the Arizona Sun Corridor; Interstate 15, which runs northeast through the Inland Empire to Las Vegas and Salt Lake City; and Interstate 805, which splits from I-5 near the Mexican border and rejoins I-5 at Sorrento Valley. Major state highways include SR 94, which connects downtown with I-805, I-15 and East County; SR 163, which connects downtown with the northeast part of the city, intersects I-805 and merges with I-15 at Miramar; SR 52, which connects La Jolla with East County through Santee and SR 125; SR 56, which connects I-5 with I-15 through Carmel Valley and Rancho Peñasquitos; SR 75, which spans San Diego Bay as the San Diego-Coronado Bridge, and also passes through South San Diego as Palm Avenue; and SR 905, which connects I-5 and I-805 to the Otay Mesa Port of Entry. The stretch of SR 163 that passes through Balboa Park is San Diego's oldest freeway, and has been called one of America's most beautiful parkways. San Diego's roadway system provides an extensive network of cycle routes. Its dry and mild climate makes cycling a convenient year-round option; however, the city's hilly terrain and long average trip distances make cycling less practicable. Older and denser neighborhoods around the downtown tend to be oriented to utility cycling. This is