M0 Budapest ring road

Chainage km 0–13.9 (M1 to Road 6), opened 3 May 1994 as a 2x2 road. Widened to 2x3 lanes in two steps: M1 km 2.84 – M6 (6.56 km, Colas Hungária Zrt., net contract HUF 11.11 billion), opened 19 June 2012, and M1 – M7 (2.725 km, Betonútépítő Zrt., net contract HUF 6.38 billion), opened 23 November 2015. The M6 – Road 51 widening of 2013 also covers the part of this lot east of the M6 junction.

Chainage km 13.9–23.2, the first part of the ring that is still on the M0, opened 16 November 1990 as a 2x2 road. It includes the Deák Ferenc Bridge over the Danube (770 m) and the Soroksár bridge over the Ráckeve Danube branch (499 m). Widened to 2x3 lanes between the M6 junction and Road 51 (11.06 km, M-0 déli ág II. Konzorcium, net contract HUF 37.03 billion), opened 30 June 2013.

Chainage km 23.2–29.5, a new 2x3 alignment that links the older south sector to the east sector and cut the route by 4.2 km. Before it opened, the M0 ran from Road 51 to the M5 along the 1988 road that is now the M51, and the east sector began on the M5. The M51 name was applied on 31 August 2013.

Chainage km 29.5–42.2, opened 17 December 2005 together with the 12.5 km Vecsés–Üllő bypass of Road 4. NIF says both sections took 17 months to build and that Strabag built the section; the release gives HUF 33.8 billion and HUF 12.5 billion without saying clearly which road each covers, so no cost is recorded. hu.wikipedia says the M5 – M3 stretch has concrete pavement.

Chainage km 42.2–68.7, opened 16 September 2008. NIF announced the start of construction on 13 March 2006 and planned completion for the end of 2007. The release names the "ED"-M0 joint venture for the stretch between Road 3 and the M3, and PVT-M0 for the second and third sub-sections (6.7 km and 10.9 km); the first sub-section is not named in the text. The client was Nemzeti Autópálya Zrt. The EUR 284 million is a budget, not an outturn, so no cost is recorded.

Table chainage km 69.65–72.54. Opened 16 June 1999 as a 2x2 road with a median and hard shoulders, with five junctions on the M3 – Road 2 stretch. Unitef '83 made the design phases for the M3 – Road 11 sector. hu.wikipedia's M0 article gives 1998 for the M3 – Road 2 opening; the section table, which cites 1999 press, is followed here.

Table chainage km 72.54–75.6. Opened 29 October 1999 as a 2x2 road, the continuation of the M3 – M2 lot. The two lots were known as Roads 2/B and 2/A before the ring was joined up.

Table chainage km 72.835–76.709, opened 30 September 2008. The Megyeri Bridge between Újpest and Budakalász (km 74.526–76.387, 1861.35 m, five bridges and nine structures, designed by Unitef-Céh Kkt.) is inside this lot and is entered as its viaduct length; the consortium named is the bridge's builder. It was handed over on 30 September 2008 and went into traffic on provisional permits, built for 2 x 2 lanes with room for 2 x 3. hu.wikipedia gives HUF 63 billion as the bridge's total construction cost, with no price year or VAT basis; it covers the bridge, not the whole lot, so no cost is recorded. The drawn centreline is about 15% shorter than the tabled length: it starts at the OpenStreetMap node of the Road 2 junction and ends where the westbound carriageway ends.

en.wikipedia: the 9 km section between Highway 11 and Highway 10 is planned but construction is not scheduled. The drawn line is OpenStreetMap's proposed route (relation "M0 északnyugati szektor Plan-A"), 7.3 km between the Road 11 end and the Road 10 crossing, so about 19% shorter than the stated length. The planning table on hu.wikipedia gives 8.040 km for the same section, against 7.346 km between its chainage points (km 76.709 and 84.055); the drawn line starts about 0.5 km west of the end of the Road 2 – Road 11 lot. hu.wikipedia says design of the west sector began in 2018 and the project came off the agenda early the next year; it also gives an estimate of nearly HUF 400 billion for the whole west sector, with no price year.

en.wikipedia: the 18 km remaining section between Highway 10 and the oldest part of the M0 at the M1 interchange. The drawn line is OpenStreetMap's proposed route (relation "M0 északnyugati szektor Plan-A"), 18.3 km from the Road 10 crossing to the end of the built M0 near the M1. The west sector is mostly tunnel and viaduct, per the junction table on hu.wikipedia (planned tunnels of 2020 m and 3190 m). It is not on the Trans-European network, so it would need national funding, according to hu.wikipedia.