A French firm has developed honeycombed thermoplastic blocks that retain storm water under curbside surfacing materials, discharging stored water gradually into the storm system. Test installations have proven effective in preventing drainage ponding and backup.

ADAAG 4.7.5 Sides of Curb Ramps.
If a curb ramp is located where pedestrians must walk across the ramp, or where it is not protected by handrails or guardrails, it shall have flared sides; the maximum slope of the flare shall be 1:10 [...].