Source 1:

https://www.gigacalculator.com/articles/what-is-the-average-speed-of-different-modes-of-transportation/

These are the average speeds of some common modes of transportation:

Commercial passenger aircraft: 547 to 575 miles per hour
Private jet: 400 to 711 miles per hour
Europe high-speed rail: 155 to 217 miles per hour
Shinkansen (Japanese bullet trains): 150 to 200 miles per hour
Modern cruise ship: 23 to 27 miles per hour
Bicycle: 10 to 24 miles per hour
Sailboat: 4.5 to 7 miles per hour
Walking: 3 miles per hour

Source 2:

https://www.researchgate.net/figure/Average-travel-speeds-in-each-survey-year-and-standardized-mode-speed_tbl1_338604360

Source 3:

https://wonderlearning.blog/real-average-speed-us-train-facts

When people think of passenger trains, they often envision swift, efficient travel. However, the operational reality for Amtrak, the primary passenger rail operator in the United States, is far more nuanced. While its locomotives are capable of impressive speeds, the average journey speed for most passengers is surprisingly modest, often hovering between 50 and 60 miles per hour, with long-distance routes averaging even less.

So we have:

D = deaths per billion miles. S = speed in miles per hour.

If we first solve for and find the time taken to travel one billion miles at speed S, we would do:

T = 1,000,000,000​ / S

(T is time in hours)

What we want is D / T

D / T = D / ( 1,000,000,000 / S)

->

D / T = (D * S) / 1,000,000,000

So, that's our rough conversion.

You may have noticed that Aircraft are now more dangerous than Buses, Subways, med/long distance Trains, and are only ~2x safer than Ferries, not ~45x times safer, as they are with the OP metric.

One hour of Motorcycles transit, on the other hand, is now ~29x more deadly than an hour of car transit, ~276x more deadly than an hour of aircraft transit...

... as opposed to the OP metric, where a billion miles of motorcycle travel is again ~29x more deadly than a billion miles of car travel, but is ~3039x more deadly than a billion miles of aircraft travel.

Probably also worth noting that this is only deaths, not injuries, say, requiring hospitalization.

I imagine doing deaths + serious injuries would also change this graph significantly.

Also also, this doesn't take into account road rage that does not directly involve the vehicle, I don't think.

It does not include injuries or deaths on some form of public or mass transit where say, you get assaulted by another passenger, or something like that.

That could also tweak things, potentially, but I have no strong instinct about if it would really matter, or how... and, you could again do deaths vs deaths + serious injuries.