To attend the IBM Programming Language Day on May 7, I rode my bicycle from New York City to Hawthorne and back. It was a good ride as always. Here is my route, based on the NYCC route to Tarrytown.

Take the 4 train uptown to the last stop Woodlawn
N on Jerome
R 233 St
1st L Van Cortlandt Park E stay straight for over 4 miles [becomes Kimball Ave; cross Cross County Pkwy; cross Sprain Brook Pkwy; cross Palmer Ave]
R Pondfield
2nd L Parkview (before overpass)
BR at stone church
L Scarsdale Rd—to end (about 1 and 1/2 mi)
R Ardlsey [becomes Popham] into Scarsdale (good snack stop)
after bridge into Scarsdale, turn left and pass the train station (East Parkway)
R Crane (for half block) [instead of getting onto Bronx River Pkwy]
L Fox Meadow [becomes Walworth Ave, Fisher Ave, Bank St, Ferris Ave]
stay straight for 3-4 miles
pass White Plains train station
center lane—continue straight up hill
L at T [after Cross Westchester Expy (I-287), onto Cemetery Rd]
cross Bronx River Pkway
up steep hill onto Old Tarrytown Rd
jog R on Hillside Ave S (RT-100); continue on Old Tarrytown Rd
R onto Knollwood Rd (RT-100A)
L onto Grasslands Rd (RT-100) before Knollwood Rd becomes Bradhurst Ave
pass Sprain Brook Pkwy
R onto Walker Rd
L onto Dana Rd then R onto Saw Mill River Rd (RT-9A)
next R onto Skyline Dr

My return route was simple:

S on Saw Mill River Rd (RT-9A)
Keep going for a long time
Get slightly lost then onto S Broadway (RT-9) to the 1 train at 242 St

If the hours during which Metro-North allowed bicycles on board were not so restrictive, I would have taken the train to Hawthorne then biked as follows.

R (S) on Elwood Ave [Pass 141, E Cross St, Pearl St, Milford St]
R on Chelsea St [Before Frankford St, Home St, Main St, Bradford St] [Pass Taconic State Pkwy, …, Bradhurst Ave (RT-100)]
L on Pythian Ave [Pass Broad St, Astor Ave, Weed Ave, Serrano Ave]
R on Belmont Rd
L on Philip Pl [Before Saw Mill River Rd (RT-9A)]
R on Stevens Ave
L on Old Saw Mill River Rd S
Sharp L on Nilsson