Electric bikes and scooters now account for more than half of all vehicle-related trauma cases at one of New York City's busiest hospitals — a share that stood below 10 percent just five years ago.

That figure, drawn from a study published April 15 in *Neurosurgery*, captures how rapidly the math of urban injury has shifted. Researchers at NYU Langone Health analyzed 914 patients treated at NYC Health + Hospitals/Bellevue between January 2018 and August 2023 for injuries linked to both pedal-powered and electric micromobility devices. One-third suffered traumatic brain injury. More than two-thirds required hospital admission. Roughly 30 percent needed intensive care.

The study lands at a moment when cities worldwide are expanding bike-lane infrastructure and delivery platforms increasingly depend on e-bikes for last-mile logistics. Its core finding — that the clinical burden of micromobility is growing faster than the safety infrastructure meant to contain it — poses a direct challenge to policymakers who have treated the two as separate tracks.

Collisions with cars or trucks caused roughly half of all injuries, the researchers found. Fewer than one-third of riders wore helmets, and helmet absence was directly linked to higher rates of brain and facial trauma. About one in five patients tested positive for alcohol, a factor associated with both worse neurological outcomes and lower helmet use.

The finding that drew particular attention from the study's authors involves pedestrians. The 69 pedestrians struck by electric bikes or scooters in the dataset suffered brain injuries at nearly double the rate of riders themselves — a disparity the researchers described as a signal that current safety conversations are too narrowly focused on those behind the handlebars.

"Our study shows that micromobility injuries are producing serious brain and spinal trauma that demands neurosurgical care at a scale we haven't seen before," said Hannah Weiss, a neurosurgery resident at NYU Grossman School of Medicine and the study's corresponding author. She identified helmet mandates, protected bike-lane design, and enforcement as the measures most likely to reduce surgical caseloads.

Injury timing added another layer of specificity to the findings. Cases peaked between 6 and 8 p.m., a window that aligns with the heaviest concentration of e-bike food delivery traffic in dense urban neighborhoods. That pattern suggests the injury burden is not randomly distributed across the day but clusters around commercial delivery activity — a consideration that regulators have not yet systematically addressed.

Paul Huang, chief of neurosurgery at NYC Health + Hospitals/Bellevue, called for multi-city studies to determine whether interventions such as protected lanes and helmet programs translate into measurable reductions in surgery rates. The Bellevue data are drawn from a single institution, and the researchers acknowledged that their findings may not generalize uniformly across cities with different infrastructure profiles or enforcement regimes.

What the data do establish is a rate of change that outpaces most public health responses. Micromobility device use in American cities expanded sharply after 2018, driven by app-based rental platforms, post-pandemic shifts in commuting, and the explosive growth of gig-economy delivery. Regulatory responses — helmet laws, speed caps on e-bikes, lane requirements — have varied widely by city and state, and enforcement has been inconsistent even where rules exist.

The Bellevue study does not attempt to resolve those policy questions, but its trajectory is difficult to set aside. A trauma category that represented fewer than one in ten emergency cases in 2018 and now accounts for more than one in two is, by any measure, a system under pressure. Whether that pressure translates into coordinated action — on helmet enforcement, lane design, or the operating conditions of delivery platforms — remains, for now, an open question.