5 of the Most Expensive Highways Ever Built

How expensive can it be to lay a road? The answer is likely more than you think. Along with the construction of the roadways themselves, there are many other factors to take into consideration, such as the price of the land and the cost of carrying away excavated earth. Then, there are the bridges and tunnels required to span any waterways or railroads along the route, as well as the need to divert utilities such as water pipes and electricity cables. And getting the project approved in the first place involves planning costs and fees for engineering consultations, not to mention funding for architect-drawn plans. It’s little wonder, then, that the final cost for the world’s greatest highway projects runs in the billions of dollars. Here are five of the most expensive highways ever built.

5. Marina Coastal Expressway – Singapore

Estimated cost of construction: $4.3 billion USD

Singapore’s 3-mile-long Marina Coastal Expressway took five years to complete, opening in 2013. The main reason for the lengthy build is that a significant proportion of this five-lane highway consists of a 1,378-foot-long tunnel, part of which is underwater. At its deepest point, the road runs 66 feet beneath the seabed south of the Marina Barrage. The unpredictable currents and soft ground — comprising marine clay, alluvium, and infill material — made the build difficult.

Techniques employed to keep it stable and watertight didn’t come cheap, which helps to account for the road’s high price tag. An article in The Straits Times stated it totaled $4.3 billion, making it the most expensive road in Singapore when calculated per mile. However, the build quality of the Marina Coastal Expressway is reported to be exceptional, with the smoothness of the surface achieved by cutting-edge laser technology.  

4. Gebze-Orhangazi-İzmir Motorway – Turkey

Estimated cost of construction: $7 billion

The goal of this ambitious project was all about linking western Turkey’s major cities. The Gebze-Orhangazi-İzmir Motorway was built to reduce distances and travel times between Istanbul, Bursa, Balikesir, Manisa, and Izmir, as well as to improve connectivity between the Aegean coastline and Istanbul. Construction cost an estimated $7 billion, with an additional $4 billion to cover operating and maintenance costs until 2035. 

This toll road, the most costly of its type in the country, is referred to locally as the O-5. It has been fully open since 2019 and carries about 40,000 vehicles each day. Along its 264-mile length, there are 38 viaducts and several miles of tunnels, but the most spectacular aspect is the Osman Gazi Bridge, a 5,085-foot suspension bridge over İzmit Bay. It is one of the longest bridges in the world when measured by its central span.  

3. Egnatia Odos Motorway – Greece

Estimated cost of construction: $8.4 billion

Coping with the mountainous terrain also had a significant effect on the costs of the Egnatia Odos Motorway in Greece, also known as the A2. The final bill is estimated to be about $8.4 billion. Half the money came from the European Union’s coffers, while the rest was funded by the Greek government, the European Investment Bank, and the European Commission’s Community Support Framework. The project was started in 1994 and finished in 2009.

Supporters argue that the highway brings multiple benefits to the region, including improving connectivity with the rest of the EU, attracting investment and further industrial development, and tapping into the emerging Balkan market. It is also hoped that the motorway will further open up this part of northern Greece to tourism and reverse the trend of rural depopulation. 

2. Adler-Krasnaya Polyana Highway – Russia

Estimated cost of construction: $9.4 billion

The Adler-Krasnaya Polyana Highway was a crucial part of the 2014 Sochi Olympics infrastructure build, linking the coastal city with inland ski resorts more than 1,600 feet higher in elevation. The project ended up costing an estimated $9.4 billion to construct a road that was just 25 miles long. 

The challenging terrain of the Caucasus Mountains proved to be a headache for engineers tasked with tackling issues relating to the local geology. Six boring machines and 14 vehicles to carry out the rock that had been excavated added to the mounting costs. However, in green-lighting its construction, the Russian government hoped it would act as a catalyst for further development in the region and make the interior more accessible. Nevertheless, opponents remain critical of its soaring costs and also its negative impact on the local ecology.

1. Boston’s Central Artery/Tunnel Project – Massachusetts

Estimated cost of construction: $14.8 billion

Boston’s Central Artery/Tunnel Project, nicknamed the Big Dig, is widely considered to be the most expensive highway ever built. Official sources put the total cost at about $14.8 billion, though some commentators argue the figure could be as much as $24.5 billion.

The original Central Artery was an elevated highway that ran directly through downtown Boston. It became no longer fit for purpose: Congestion was the norm, and the road experienced an accident rate four times the U.S. national average. 

Construction began in 1991 on a new underground expressway leading to two bridges that span the Charles River. One of them is the 10-lane Leonard P. Zakim Bunker Hill Bridge, one of the widest cable-stayed bridges in the world. In addition, links to Logan International Airport were improved with the extension of Interstate 90. Once the project was complete, the old elevated highway could be demolished. In its place, a broad swath of parkland was developed, reconnecting Boston residents to their waterfront.