Dual-Track Electrification in a Dense City: The Asymmetric Diffusion of Electric Cars and Two-Wheelers and the Role of Public Charging Infrastructure

Electric cars and electric two-wheelers are transforming urban mobility along two parallel tracks, yet the two are usually studied separately, and evidence from a single policy environment in which both diffuse simultaneously remains scarce. Using monthly full-population vehicle registration records for 2000–2026 and official public charging and parking statistics from Macao, we compare the diffusion dynamics of the two tracks within one dense city. Threshold-crossing analysis shows that around the 2022 replacement subsidy and the accompanying build-out of public charging spots, the electric share of new two-wheeler registrations rose from 5% to 25% within 18 months, less than half the 37 months taken by cars; from 2024 to 2026, the two-wheeler share reached parity with and in most months exceeded that of cars. Lead-lag tests indicate that charging-spot expansion precedes two-wheeler fleet growth (Granger lag-1 p = 0.030; unfiltered distributed-lag joint p < 0.001), a pattern that weakens under seasonal adjustment and detrending (p = 0.186); no such precedence appears on the car track. Ample car parking plausibly favors private charging—a hypothesis, not a measured mechanism: parking spots do not establish charger access. Where two-wheelers are numerous and private parking scarce, public charging may enable their electrification, pending charging-access data.