Ellenbrook. A shared pedestrian and bicycle path is built alongside most of Tonkin Highway; namely between Muchea and Hale Road, as well as south of Mills Road East. In most other sections, the highway's sealed shoulders also function as bicycle lanes. Main Roads Western Australia monitors traffic volume across the state's road network, including several locations along Tonkin Highway. The section near Perth Airport, south of Great Eastern Highway, is the busiest, averaging over 56,000 vehicles per weekday in 2007–08, and over 57,000 in 2008–09. North of the Swan River, the traffic volume gradually decreased to under 40,000 vehicles per weekday near the northern terminus, in 2007–08. Measurements in 2008–09 showed the lowest volume to be under 10,000 vehicles per weekday near the southern terminus, north of Thomas Road. In 2013, immediately preceding the upgrade of Tonkin Highway's central section to a six-lane freeway-standard road, junctions in and around Kewdale, Forrestfield and Perth Airport carried traffic volumes beyond their capacity during peak periods. Average peak period traffic speeds in this part of Tonkin Highway were measured as or less in 2013. The slowest section was from Leach Highway to Horrie Miller Drive, which recorded an average of during the afternoon peak period. Traffic volume, exceeding 50,000 vehicles per day in 2012, is forecast to almost double by 2031. Traffic modelling showed that leaving the current network of traffic light controlled intersections in place would have resulted in gridlock by 2021. Following the completion of the Gateway WA project in 2015, the upgraded road network is forecast to have an average speed in peak periods of between in 2021. Muchea to Ellenbrook Tonkin Highway commences at a roundabout interchange with Brand Highway and Great Northern Highway near the town of Muchea in the Shire of Chittering of the Wheatbelt region. The highway is a continuation of Great Northern Highway to/from the north of Western Australia with direction signage including Port Hedland some away. The interchange is characterised by both the installation of curvy green street lighting known as "wiggle poles" on both the bridge passing over the roundabout as well as on the westbound approach to the roundabout as well as a large road train assembly area to the southeast of the interchange. After , Tonkin Highway passes over the old Brand Highway connection between Muchea and Great Northern Highway (now known as Granary Drive) before curving to the southwest to