Civil Engineering Female Student Looking through tunnel like structure

The Central Artery

UMass Lowell Image

What is it?

Largest,most technically challenging
Most expensive public works project in US history($13B counting) 
Third tunnel (Ted Williams) to Logan Airport
10-lane cable-stayed bridge over Charles River 
New access bridge over Charles River 
Depress Central Artery below ground 
Reclaim land under current elevated Central Artery as park land

Why build it? 

I-93 (Southeast expressway) originally designed for 75,000 trips/day;
By 1990,  it was 192,000 trips/day 
Ttraffic from west wants to go to Logan or downtown 
Traffic from south wants to go to Logan or downtown 
Ttraffic from north wants to go to Logan or downtown  
Local traffic wants to stay local 
All the above currently share I-93 in downtown Boston

Why is it so expensive?

One-third of cost is “mitigation” - keeping the CA/T neighbors satisfied 
Construction continues without disrupting existing highway(s) 
Commuter rail & subway public transit systems active during construction 
Federally protected waterway
And much existing infrastructure in place during construction !