change scattermapbox symbols

I would like to change the symbol in a scattermapbox but so far I have been unsuccessful. I suppose that I am just not using the right syntax, but I have not been able to get any hints from the documentation.

dat <- tibble::tribble(~latitude, ~longitude,
 "39.33359", "-76.63563",
 "38.85391", "-76.90812",
 "39.39105", "-76.83006")

fig <- dat  %>%
      plot_mapbox(
        lat = ~latitude,
        lon = ~longitude,
        mode = "markers",
        marker = list(symbol = 'car', size = 15, color='blue'),
        type = 'scattermapbox') 
fig %>%
    layout(
      mapbox = list(
        style = 'open-street-map',
        zoom = 5,
        center = list(lat = 39.33359, lon = -76.63563)))

It works fine with the default shape (circle).
Any idea?

No repository files or tests are named. Start by reproducing the supplied R example and checking the scattermapbox marker-symbol documentation; done means identifying the supported syntax or documenting that the requested symbol is unavailable, with a working example or a clear limitation.