Why Baldwin Street’s Upper Slope Needs a Stiffer Surface
A road surface on a steep hill is pushed not only from above by vehicle weight, but also along its length. As cars climb, brake, or start moving, their tires apply forces that can tug at the pavement. Gravity adds a steady downhill pull to the road’s own materials and to traffic using it.
Asphalt is a mixture of mineral aggregate bound together with bitumen, a substance that softens as it gets warmer. Under repeated loads, softened asphalt can slowly shift—a kind of deformation called creep. On a sharp incline, that movement can show up as ruts or ridges where tires repeatedly press and grip.
Concrete Resists Movement
Concrete behaves more like a rigid slab. It is less prone to slowly flow under heat and traffic, so it can better hold its shape where the slope makes sideways and downhill forces especially important. That stiffness is the practical advantage on Baldwin Street’s upper section: the pavement must resist being nudged out of place, not merely cover the ground.
A rigid surface has its own demands, including managing cracks as the material expands and contracts. But pavement choices are local engineering decisions. On a flatter road, asphalt’s flexibility and ease of repair may be useful; on a steep stretch, resistance to deformation can matter more. Baldwin Street makes that tradeoff visible underfoot.
