For the last three decades, millions of American parents have been able to park their minivans between parallel white lines – avoiding the spaces with the blue and white logos that depict a stick figure in a wheelchair – and usher their child into a stroller, which they can push up a portion of the curb gradually sloped from the asphalt up to the sidewalk, before guiding the stroller up a concrete ramp and through an entrance wide enough to fit it.