A multi-lane interstate curving through a hazy, tree-covered mountain pass with houses on the hillside beyond

Sustainable Highways

How roads are designed, paid for, built and kept in service, and the standards, studies and agency decisions behind each of those.

Each piece works from federal tables, state design manuals and audit files, and marks the point where they stop answering the question.

HIGHWAYS

What Makes a Highway Sustainable?

Ask what makes a road sustainable and the federal reference document on the subject answers by declining to define the term. What it offers instead is a set of trade-offs between service life, lifecycle cost, how far the material traveled and the conditions the road has to survive, and no project maximizes all of them at once. The piece works through the weightings FHWA built into its own criteria, the case for putting durability above nearly everything else, and the questions no scoring framework has managed to answer.

A close-up of cracked, weathered asphalt pavement with scattered fallen leaves

Latest analysis

HIGHWAYS

What a Mile of Interstate Actually Costs

One federal table prices a lane mile of new Interstate at anywhere from $3.55 million rural to $85.85 million urbanized, and within rural mileage terrain moves the number more than road class does.

BRIDGES

The State of America's Bridge Inventory

Bridges rated Poor have dropped from 47,054 to 41,685 since 2018 while the inventory itself grew, which is not the story the repair backlog figure tells on its own.

ENVIRONMENT

What Wildlife Crossings Actually Reduce

Fourteen years of monitoring on one Montana corridor explains why published reduction percentages differ so widely. Fence length decides the outcome, not structure count.

SAFETY

What the U.S. Roadway Fatality Data Shows

Two federal death tolls exist for 2023, 40,901 and 41,025, and the gap is a documented feature of how the fatality file closes a year rather than anybody's error.

FREIGHT

Which Freight Corridors Matter Most

No federal product ranks them, because the designated network, the flow model and the truck-GPS delay tables were each built to answer a different question.

TECHNOLOGY

How EV Charging Reshapes the Interstate

The federal charging rule sets a 600 kilowatt floor per station, which makes a funded site an electrical service question long before it is a real estate one.

A nighttime aerial view of an asphalt paver and roller laying fresh pavement on a highway lane, lit by work lights

Materials and Pavements

Asphalt vs. Concrete for Highway Construction

Federal regulation asks only that a pavement be safe, durable and reasonably priced, which leaves the choice to lifecycle arithmetic, traffic class and maintenance capacity.

Long-Life Pavement: Designing Roads That Last

A forty-year pavement is specified as a list of distresses it must not develop, with published thresholds down to the share of slabs allowed to crack.

How Recycled Asphalt Is Used in Road Projects

Almost all reclaimed pavement goes back into a road, yet it still averages under 22 percent of a new mixture, and the reason is a binder that has aged twice.

Safety

How Road Engineers Reduce Work-Zone Crashes

Federal counts put 891 deaths in work zones in 2022, of which 94 were highway workers. Most of the dead are people driving past the work, not the crew inside it.

Guardrails, Barriers and Roadside Design

Shielding ranks fourth of five roadside options, because a barrier is itself an object a vehicle can strike, and a resurfacing overlay lowers every rail it passes.

Commercial Truck Safety on the Interstate System

Large-truck crashes killed 5,340 people in 2024 and 920 of them were riding in the truck, a split that has hardly shifted across ten years of federal data.

Sustainability

How Highway Projects Measure Embodied Carbon

One mile of pavement yields three defensible carbon totals, and the grant money for low-carbon materials is awarded on the shortest, which stops at the plant gate.

Understanding Highway Lifecycle Cost Analysis

The federal primer on the method runs an example with two answers: one alternative is cheaper for the agency, the other once driver delay is priced in.

INVEST, Envision and Greenroads Compared

Envision awards its highest rating at half the applicable points, and published evidence that any of the three systems changed a road is thinner than it looks.

Freight and Transportation

Why I-35 Is Critical to U.S. Freight

The route begins at a bridge over the Rio Grande in downtown Laredo, where the state recorded more than two million trucks entering the country in 2015 alone.

The National Truck Parking Shortage, Explained

The second national inventory counted roughly 313,000 spaces, and the metric meant to size the shortage measures demand with a row that counts the wrong trucks.

How Commercial Trucking Shapes Highway Design

Lane widths key off truck counts, clearances trace to a Defense Department requirement, and pavement thickness rests on a model fitted at a road test that ended in 1960.

Technology

Photo: David Herrera, CC BY 2.0

What Intelligent Transportation Systems Do

Wyoming runs 160 variable speed limit signs off 95 sensors on I-80, so the signs outnumber the measurements feeding them by five to three.

Connected Vehicles and V2X: The Road Talks Back

A nine-vehicle pileup in Arkansas fog in 1995 set this research going. Thirty years later the roadside radios it produced are losing their licenses instead of scaling up.

Digital Twins for Highways and Bridges

Two national definitions of a digital twin landed in 2024 and they do not agree, which is most of why the term travels further than the evidence for it.

Projects and case studies

Nationwide

The Largest Highway Builds Under Way

Four megaprojects publish four different kinds of cost figure, and only one of them states its total to the dollar.
Cincinnati and Covington

The Brent Spence Bridge Corridor Project

A 1985 decision to buy a fourth lane by deleting the shoulders is being undone at a cost of several billion dollars.
Hampton Roads, Virginia

The Hampton Roads Bridge-Tunnel Expansion

Nineteen years separate the record of decision from full notice to proceed, and the risk register prices the ground itself.
Boston

The Big Dig's Lessons for American Megaprojects

The first quantity to move on this project was not the cost but the boundary of the estimate, and two federal reporting regimes exist because of what came next.