of the region's network of High Occupancy Vehicle (HOV) lanes. This practice was pioneered at Seattle Transit as the Blue Streak express bus service running between Northgate Park & Ride and Downtown Seattle. Special stops called "freeway flyers" or freeway stations were constructed to allow efficient transfer between local and express buses. The first freeway flyer stop opened in 1975 at Montlake Boulevard and State Route 520. Metro also takes advantage of new HOV direct-access ramps and freeway stations constructed by Sound Transit to improve speed and reliability of its commuter routes. Skip-stop spacing Metro uses skip-stop spacing on 2nd, 3rd, and 4th Avenues in Downtown Seattle, whereby buses skip every other bus stop. On 3rd Avenue, each bus route is assigned to Blue, Yellow, Red or Green stop groups and each bus stop has two color designations; in the northbound direction, every other bus stop is a Red/Yellow or Green/Blue stop, while in the southbound direction they are Green/Yellow and Red/Blue. On 2nd and 4th Avenues, routes are grouped into Orange and White stops. The bus stop color groupings are identified by a colored plate installed above or on the side of the bus stop sign. On 3rd Avenue only, there are additional colored markers one block ahead of each bus stop on the trolley overhead wires, to help bus drivers identify the colors of the upcoming bus stop. Night Owl services Metro operates a network of 12 routes with late-night "Night Owl" service, which is defined as having regular service between midnight and 5 am. The Night Owl network is made up of some of Metro's most popular routes, and is designed to connect neighborhoods with major transportation hubs including downtown Seattle, Sea–Tac Airport, park & ride lots, transit centers, and Link stations (providing service during the hours when trains are not in service). The City of Seattle's transportation benefit district funds service on Night Owl routes that operate entirely within the city limits. Routes with Night Owl service include the 7, 36, 48, 49, 120, 124, 160, 161, and the RapidRide A, C, D, and E Lines. Trailhead Direct King County Metro operates a weekend express shuttle between Seattle and hiking areas in the Cascade foothills called Trailhead Direct from April to October. The service, operated in partnership with the county's park and recreation department and private companies, debuted in 2017 and was expanded the following year