  The relative velocity distribution of wide binary (WB) stars is sensitive to
the law of gravity at the low accelerations typical of galactic outskirts. I
consider the feasibility of this wide binary test using the `line velocity'
method. This involves considering only the velocity components along the
direction within the sky plane orthogonal to the systemic proper motion of each
WB.
  I apply this technique to the WB sample of Hernandez et. al. (2019),
carefully accounting for large-angle effects at one order beyond leading. Based
on Monte Carlo trials, the uncertainty in the one-dimensional velocity
dispersion is $\approx 100$ m/s when using sky-projected relative velocities.
Using line velocities reduces this to $\approx 30$ m/s because these are much
less affected by distance uncertainties.
  My analysis does not support the Hernandez et. al. (2019) claim of a clear
departure from Newtonian dynamics beyond a radius of $\approx 10$ kAU, partly
because I use $2\sigma$ outlier rejection to clean their sample first.
Nonetheless, the uncertainties are small enough that existing WB data are
nearly sufficient to distinguish Newtonian dynamics from Modified Newtonian
Dynamics. I estimate that $\approx 1000$ WB systems will be required for this
purpose if using only line velocities.
  In addition to a larger sample, it will also be important to control for
systematics like undetected companions and moving groups. This could be done
statistically. The contamination can be minimized by considering a narrow
theoretically motivated range of parameters and focusing on how different
theories predict different proportions of WBs in this region.
