For people visiting to Japan, it would be unbelievable not to go to the center of Tokyo by not using any public transportation methods, but it is not so difficult.
It is about 12km from Haneda airport to Shinagawa station. You can find and enjoy "Former Tokaido" through the path. Let's try!
羽田空港からの徒歩ルートを紹介。旧東海道を通ると交通量も少なく、楽。約12km。SFC修行は運動不足になりがちなので、おすすめ。
I'd like to explain about the points to take.
ポイントとなる場所は以下。（追々、詳細記載予定）
1) After going out from exit of the international terminal, turn to right and go straight. (If you are in domestic terminal, firstly you take free bus running between 3 terminals and get off the bus stop of International terminal)
・国際線ターミナルを右手に進む 。（国内線から来た場合は、無料連絡バスに乗って国際線バスターミナルへ向かう）
2) You encounter "T" cross over point as the photo shows, turn to left. (Walking to right direction is prohibited...)
・T字突き当りを左へ。（右は車以外通行禁止）
3) After finding "Kuronogate" on the right side, at the cross over point of "Haneda Asahi-cho" as the photo shows, turn to right.
・羽田旭町交差点を右折（クロノゲートを通った先の交差点）
4) After passing the bridge and take curve to the right direction, you find the croo over point as the photo shows, then turn to left. (If you turn to right, you find the Ikegami driving school as the ad shows...)
・橋を渡って右にカーブしたところの交差点を左折
（右折すると池上自動車教習所の看板）
5) This point is a little bit difficult.
As the photo below shows, turn to right and soon turn to left and go straight.
(Around "Omori Higashi 5 chome")
・貴船堀緑地右の道路を入り、まっすぐ（大森東5丁目付近。写真を右折し、すぐ左折し道路を入る）
6) After passing the bridge and go straight, you encounter "Sawa medical shop (サワ薬品)", turn to right. Then you take "Former Tokaido".
・橋を渡りさらにまっすぐ行くとサワ薬品に突き当たるので、右折し旧道へ。
7) Please enjoy the atmosphere of retro post stations.
・風情ある宿場町の様子をお楽しみください。
8) You can join with the main street of "Dai ichi Keihin", and go straight. At the former "Suzugamori execution chamber", take the former Tokaido again.
・第一京浜に合流後、直進。鈴ヶ森刑場のところで再び旧道へ入る。
9) Please enjoy the atmosphere of retro post stations again.
・再び、風情ある宿場町の様子をお楽しみください。
10) After pass through crossing near Kita-Shinagawa station, turn to right. You can find Keikyu Wing building. (One of the landmarks of Shinagawa)
・北品川駅傍の踏切を渡り、右方向へ。品川の京急WINGも見えてくる。
11) You can arrive at Shinagawa station.
・品川駅へ。 
Have a safe trip!
