With a whopping cost of $24bn, Big Dig is the most expensive highway project in the world. Road Traffic Technology lists the top ten of the world’s costliest expressways, based on their project cost.

World’s costliest expressways: Top ten by project cost

1. The Big Dig – $24bn

2. Karachi-Lahore Motorway – $11.5bn

3. Sochi Highway – $8.7bn

4. Egnatia Odos – $8.4bn

5. Gebze-Orhangazi-İzmir Motorway – $7bn

6. Mon-Fayette Expressway – $5.4bn

7. Marina Coastal Expressway – $3.15bn

8. Tehran-North (Shomal) Freeway – $2.2bn

9. Ionia Odos Motorway – $1.6bn

10. Durango-Mazatlan Highway – $1.4bn

1. Central Artery/Tunnel Project (Big Dig), Massachusetts, US – $24bn

World's costliest expressways
The cost of the Big Dig Highway development was approximately $24bn. Credit: Rene Schwietzke.

The Big Dig highway in Boston, Massachusetts, US, is an approximately 12km-long corridor, including more than 257 lane-kilometres of new highway and 8km of tunnel sections.

The project replaced the old deteriorating Central Artery (Interstate-93), an elevated six-lane highway with a new underground eight to ten-lane expressway leading to a 14-lane, two-bridge crossing of the Charles River at the northern end.

The project also extended Interstate 90 (Massachusetts Turnpike) from south of downtown Boston to Boston’s Logan International Airport.

The highway reduced traffic congestion across Boston and improved the traffic flow. The average travel times between the I-90/I-93 interchange and Logan Airport reduced by up to 72% during peak hours.

The Massachusetts Turnpike Authority initiated the project in 1982. The construction work started in 1991 while the project was completed in 2007.

2. Karachi-Lahore Motorway, Pakistan – $11.5bn

World's costliest expressways
Karachi-Lahore Motorway is operated by Pakistan National Highway Authority and majorly funded by the Chinese state-owned banks. Credit: Fazeela Jamil.

The Karachi-Lahore Motorway (KLM) is a 1,694km-long, six-lane motorway, which will connect Karachi and Peshawar via Lahore and Islamabad upon completion.

The project is a major part of the China-Pakistan Economic Corridor (CPEC) and will connect major cities such as Hyderabad, Faisalabad, and Multan. The KLM is divided into seven sections, most of which have been opened to the public.

Operated by Pakistan National Highway Authority, the motorway development is majorly funded by The Export-Import Bank of China and other Chinese state-owned banks.

3. Sochi Highway, Russia – $8.7bn

World's costliest expressways
The Sochi highway was developed for the Sochi Winter Olympics in 2014. Credit: Arne Müseler / www.arne-mueseler.com.

The Sochi Highway was constructed by the Federal Highway Agency Directorate for Construction and Reconstruction of Motor Roads of the Black Sea Coast for the Sochi Winter Olympics in 2014.

The 49.8km-long roadway extends between the two Olympic venues at the Black Sea coast and the winter-sports region in the Caucasus mountains.

The roadway contains more than 29km of new tunnels between the town of Adler and the Krasnaya Polyana winter-sports region.

4. Egnatia Odos, Greece – $8.4bn

World's costliest expressways
The development of Egnatia Odos was officially completed in 2014. Credit: Christaras A.

The 670km-long Egnatia Odos motorway links the eastern Greek-Turkish border crossing at Kipoi and the western port of Igoumenitsa that connects Greece with Italy. The motorway comprises several bridges and tunnels and forms an important part of European route E90.

Developed by the state-owned Egnatia Odos AE, the construction of the motorway started in the 1990s and was officially completed in 2014.

The motorway provides uninterrupted trade connectivity between the major economic and industrial hubs in the eastern and western regions of the country. It improved the trade and travel within Greece and brought Epirus, Macedonia, and Thrace near Thessaloniki, the second-largest city in Greece.

5. Gebze-Orhangazi-Izmir Motorway, Turkey – $7bn

World's costliest expressways
The Otoyol 5 motorway includes 31 viaducts, two tunnels 199 bridges, 21 toll plazas, eight maintenance & operation centres, seven service areas and seven park areas. Credit: Astaldi.

Gebze-Orhangazi-Izmir, also known as Otoyol 5, is a 426km-long, two to three-lane motorway, stretching between Gebze on the North shore of Izmit Bay, and Izmir.

The motorway includes 31 viaducts measuring 18,212m-long, two 5,142m-long tunnels, 199 bridges, 21 toll plazas, eight maintenance and operation centres, seven service areas and seven park areas. It also comprises Izmit Bay suspension bridge, which opened to traffic in July 2016.

The Turkish Ministry of Transport and Infrastructure assigned the project to the OTOYOL joint venture, which comprises Astaldi and four Turkish companies, namely Nurol, Ozaltin, Makyol, and Gocay. The motorway was officially inaugurated in August 2019.

The new route halved the travel time between Gebze (near Istanbul) and Izmir from eight hours to less than four hours. The Izmit Bay bridge reduced the crossing time of Bay to six minutes from one hour and 20 minutes by road around the Bay.

6. Mon-Fayette Expressway, US – $5.4bn

World's costliest expressways
Mon-Fayette Expressway will improve the local transportation network by enhancing the efficiency of the roadway system between Jefferson Hills and Monroeville. Credit: Dougtone.

The 109km-long Mon-Fayette Expressway (Turnpike 43) encompasses four interconnected routes, between I-68 near Morgantown in West Virginia and I-376 in Monroeville, Pennsylvania, US.

Developed by Pennsylvania Turnpike Commission, the expressway will improve the local transportation network by enhancing the safety, and efficiency of the transportation from Jefferson Hills to Monroeville.

The two phases of the project were respectively opened to traffic in 2008 and 2011. Construction on the final phase is expected to begin in 2022. The expressway will boost economic development in the Mon Valley and improve regional transportation network upon completion.

7. Marina Coastal Expressway, Singapore – $3.15bn

World's costliest expressways
Marina Coastal Expressway comprises the Singapore’s first 3.5km (2mi) long undersea tunnel. Credit: Tapanuth/Shutterstock.

The Marina Coastal Expressway is a 5km-long ten-lane roadway, connecting eastern and western parts of Singapore to the newly developed part of Marina Bay in the South. The roadway comprises Singapore’s first 3.5km-long undersea tunnel.

The expressway connects motorists with three expressways, namely Kallang-Paya Lebar Expressway (KPE), East Coast Parkway (ECP) and Ayer Rajah Expressway (AYE), as well as with a new expressway link to the new downtown at Marina Bay.

Developed by Land Transport Authority, the expressway was officially opened in December 2013.

8. Tehran-North (Shomal) Freeway, Iran – $2.2bn

World's costliest expressways
The first section of the Tehran-Shomal Freeway was opened to traffic in February 2020. Credit: Telluride749.

The Tehran-North (Shomal) freeway is a 121km-long roadway comprising four sections to connect Tehran and the Chalus city in northern Mazandaran Province, Iran.

The 32km-long first section of the project, connecting west of Tehran to Shahrestanak Village, was opened to traffic in February 2020, which reduced the existing Tehran-Karaj-Chalus route by 60km. The freeway features long tunnels, advanced fanjets, bridges and concrete cladding.

Sections two and three will pass through mountainous terrain while the 20km-long section four will connect Marzanabad in Kelardasht District to Chalus.

9. Ionia Odos Motorway, Greece – $1.6bn

World's costliest expressways
Ionia Odos reduced the travel time from Antirio to Ioannina from 3.5 hours to less than two hours. Credit: Jimzoun.

The 196km-long Ionia Odos Motorway stretches from the Rio-Antirrio Bridge across the Gulf of Corinth to the Egnatia motorway in Ioannina, Greece.

The motorway includes 24 bridges with a total length of 7km, four tunnels of 11.2km long, 77 underpasses as well as 24 overpasses. The motorway passes through four counties and boosts the economic development in western Greece.

Ionia Odos reduced the driving time from Antirio to Ioannina from 3.5 hours to one hour and 40 minutes. It improved the connection to the ports of Patra, Astakos, and Igoumenitsa, as well as to the urban and rural areas such as Ioannina, Arta and Agrinio.

Built with an estimated investment of approximately $1.65bn (€1.4bn), the motorway was opened to traffic in 2017.

10. Durango-Mazatlan Highway, Mexico – $1.4bn

World's costliest expressways
Durango-Mazatlan highway contains 63 tunnels and 115 bridges including Baluarte Bridge and El Sinaloense tunnel. Credit: Panza Rayada.

The 230km-long Durango-Mazatlan highway links Durango with the Pacific coast of Mazatlan and forms a part of the Matamoros-Mazatlan corridor, which provides a connection between the Gulf of Mexico and the Pacific Coast. The highway reduces four hours of travel time between the cities of Durango and Mazatlan.

Durango-Mazatlan highway comprises 63 tunnels and 115 bridges, including the four-lane, 1,124m-long Baluarte Bridge and the 2.8km-long Tunnel ‘El Sinaloense’, the second-longest tunnel of Mexico.

Built with the total investment of approximately $1.4bn (Mex$18bn), the highway opened to traffic in October 2013.