Apparently the NHTSA stats
aren't different for babies (likely because babies are usually heavily restrained, and probably brought out in a car less e.g. don't need school runs). Below are some US NHTSA publications with detailed answers, but here's a loose paraphrase a) it's dangerous being a nonoccupant in a driveway: nontraffic backover/backing crashes caused ~460 deaths in 2008 (~300 nontraffic + 160 traffic), see [3].
b) reported fatalities per year age of child seem to be roughly constant, i.e. babies do not exhibit a higher rate of traffic deaths (probably because they're typically restrained in carseats). See [1] p5: Table 1. Passenger Vehicle Occupants Involved in Fatal Traffic Crashes, by Survival Status and Age Group, and Restraint Use, 2021. In fact, the peak is for children passengers 13+ or 15+, not babies.
c) (These do not report crash speed, or separate freeway accidents from residential roads (posters here asking about "a drive around the neighborhood"), and you'd expect people would drive babies slightly slower.) NHTSA only separately reports nontraffic accidents (e.g. parking lots). Or non-crash deaths such as hyperthermia.
[1] https://crashstats.nhtsa.dot.gov/Api/Public/ViewPublication/...
"Traffic Safety Facts, 2021 Data, Children, DOT HS 813-456"
Key Findings
• Of the 42,939 traffic fatalities in 2021 in the United States, 1,184 (3%) were children 14 and younger.
• An estimated 162,298 children were injured in traffic crashes in 2021, a 17-percent increase from 139,058 in 2020.
• Of the 26,325 passenger vehicle occupants killed in 2021 in traffic crashes, 863 (3%) were children. Of these 863 child passenger vehicle occupants killed in traffic crashes, restraint use was known for 769, of whom 308 (40%) were unrestrained.
• Of the 1,184 children killed in traffic crashes, an estimated 294 (25%) were killed in alcohol-impaired-driving crashes in 2021.
[2] From NHTSA: NCSA (National Center for Statistics and Analysis) Motor Vehicle Traffic Crash Data Resource Page https://crashstats.nhtsa.dot.gov/#/
[3] "DOT HS 811 144, November 2008, FATALITIES AND INJURIES IN MOTOR VEHICLE BACKING CRASHES" https://crashstats.nhtsa.dot.gov/Api/Public/ViewPublication/...
A backover is a crash which occurs when a driver reverses into and injures or kills a nonoccupant such as a pedestrian or a bicyclist. Backovers can occur either on a public roadway or not on a public roadway, i.e., in a driveway or in a parking lot. The former are called traffic backovers and the latter nontraffic backovers. There are also “other backing crashes” that are not backovers, i.e., they do not involve a pedestrian or other nonoccupant, that occur when, for example, a driver backs into a tree or pole or when a driver backs out of a driveway or parking space and is struck by another vehicle. Together, backover crashes and other backing crashes are referred to as backing crashes."
Look at the table on page iv.: Fatalities and Injuries, by Type of Crash, Type of Vehicle
