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Elevated autonomous freeways could need as little as one-tenth the volume of steel and concrete as traditional elevated freeways - while moving three times more vehicles than existing freeways

Why the Huge Difference?


1. Live Load (Weight Carried):

  • Freeway Bridge: Must support fully loaded semi-trucks (80,000+ lbs) moving at high speeds. The "dynamic load" (bouncing/braking) adds massive stress.

  • Autonomous Freeway Bridge: Could only need to support passenger cars (~4,000 lbs) moving even faster.

  • A structure for 80,000-pound vehicles at 60 mph requires significantly more concrete and steel—often 10 times more—than a structure designed for 4,000-pound vehicles at 120 mph.


2. Deck Thickness:

  • Freeway Bridge: The concrete deck is typically 8-10 inches thick and heavily reinforced with rebar to survive weather, salt, and millions of load cycles.

  • Autonomous Freeway Bridge: zero harmful emissions means autonomous freeways could be covered to protect from the elements

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3. Labor Costs:

  • One tenth the concrete and steel means one tenth of the labor costs and emissions, from mining to smelting, from shipping to construction

 

Bonus: Underpass

  • Freeway Bridge: Combination of large structural elements and noise prevents other commercial uses above or below from being desirable or affordable

  • Autonomous Freeway Bridge: Leaves plenty of room for parking and other commercial structures to both use the space underneath and give structural integrity to the autonomous freeway

STEEL & CONCRETE HIGH RISES VS LUMBER-FRAMED SUBURBAN HOMES 

Future of Steel-making: Costs to fall by half by 2045

First, thermodynamic estimates estimate molten oxide electrolysis could lower the cost to make steel by 40 percent (Boston Metal).

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Second, dynamic energy management will mean systems can automatically shift high-energy processes to off-peak hours when electricity is lower, potentially saving 30 percent on energy costs (or 10 percent overall).

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Third, using IoT sensors to anticipate furnace lining failures before they happen could double their uptime (saving 10 percent of overall cost).

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The compounded savings could result in steel costing half as much to make as today. A move to autonomous trucking and increasingly automated mining could cut those costs in twenty years as well.

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Given the cost of steel is typically one-fifth the cost of building high-rises, this could make new high-rises ten percent more affordable.

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