[Silly Little Cars] FYI- modulating headlights (a kind of flashing headlight) are allowed on motorcycles according to Federal Law.

[HAL]

In case you want a flashing headlight(s) on your Cushman or Interceptor, there are aftermarket circuits for this and I've even seen an Internet sight that explains how to build your own (but admits they were uncertain if it modulating within the allowed frequencies).  Note, it also needs to include a light sensor to turn it off when there are levels of light lower than a certain level.

You might also want to consider having an off switch so you can turn it off during the day in case you get pulled over too much by police who are unaware this is legal for motorcycles (or unaware that your vehicle is a motorcycle).  I'm debating on doing this as many motorcyclists believe cars notice them more with this, plus I also thought it might be a bit of fun.  

Its from the Code of Federal Regulation 49 CFR Section 571.108 S10.17.5. (revised as of October 1, 2010). You can find the text at the Government Printing Office's website at http://edocket.access.gpo.gov/cfr_2010/octqtr/49cfr571.108.htm

or I've reproduced the text below.  Have fun.  

 S10.17.5 Motorcycle headlamp modulation system. A headlamp on a 
motorcycle may be activated to modulate either the upper beam or the 
lower beam from its maximum intensity to a lesser intensity, provided 
that:
    S10.17.5.1 Modulation.
    (a) The rate of modulation must be 240  40 
cycles per minute.
    (b) The headlamp must be operated at maximum power for 50 to 70 
percent of each cycle.
    (c) The lowest intensity at any test point must be not less than 17 
percent of the maximum intensity measured at the same point.
    (d) The modulator switch must be wired in the power lead of the beam 
filament being modulated and not in the ground side of the circuit.
    (e) Means must be provided so that both the lower beam and upper 
beam remain operable in the event of a modulator failure.
    (f) The system must include a sensor mounted with the axis of its 
sensing element perpendicular to a horizontal plane. Headlamp modulation 
must cease whenever the level of light emitted by a tungsten filament 
light operating at 3000[deg] Kelvin is either less than 270 lux of 
direct light for upward pointing sensors or less than 60 lux of 
reflected light for downward pointing sensors. The light is measured by 
a silicon cell type light meter that is located at the sensor and 
pointing in the same direction as the sensor. A Kodak Gray Card (Kodak 
R-27) is placed at ground level to simulate the road surface in testing 
downward pointing sensors.
    (g) When tested in accordance with the test profile shown in Figure 
9, the voltage drop across the modulator when the lamp is on at all test 
conditions for 12 volt systems and 6 volt systems must not be greater 
than 0.45 volt. The modulator must meet all the provisions of the 
standard after completion of the test profile shown in Figure 9.
    (h) Means must be provided so that both the lower and upper beam 
function at design voltage when the headlamp control switch is in either 
the lower or upper beam position when the modulator is off.
    S10.17.5.2 Replacement modulators. Each modulator not intended as 
original equipment, or its container, must be labeled with the maximum 
wattage, and the minimum wattage appropriate for its use.
    S10.17.5.2.1 Replacement performance. Each modulator, not intended 
as original equipment, must comply with S10.17.5.1 (a) through (g) when 
connected to a headlamp of the maximum rated power and a headlamp of the 
minimum rated power, and must provide means so that the modulated beam 
functions at design voltage when the modulator is off.
    S10.17.5.2.2 Replacement instructions. Instructions, with a diagram, 
must be provided for mounting the light sensor including location on the 
motorcycle, distance above the road surface, and orientation with 
respect to the light.