During the Golden Week holidays, hubby and I had been to his ancestral home in Ichinomiya City. We had been to Ichinomiya by our car. During our return trip to Akita, we drove along Tokyo Bay Aqua-Line Highway and also took rest for some time at Umihotaru Parking Area. Tokyo Bay Aqua-Line, also known as Trans-Tokyo Bay Highway, is a unique bridge-tunnel combination across the middle of Tokyo Bay. This tolled highway forms part of National Route 409, and connects Kawasaki City in Kanagawa prefecture with Kisarazu City in Chiba prefecture. Tokyo Bay Aqua-Line has an overall length of 15.1 kilometers which includes a 4.4 kilometers long bridge and a 9.6 kilometers long tunnel underneath the bay. The bridge is the longest road bridge across sea in Japan, and the undersea tunnel is the fourth-longest underwater tunnel in the world. At the bridge-tunnel crossover point, there is an artificial island called Umihotaru which is a parking area, and is designed as a tourist attraction with restaurants, shops and amusement facilities.
The investigation to construct Tokyo Bay Aqua-Line Highway started in April 1966. But it took another 23 years to actually start the construction. The construction started in May 1989 and was completed in April 1997. The total construction cost was 1440000 million Yen. The highway was opened to the traffic in December 1997. Tokyo Bay Aqua-Line reduced the drive between two industrial regions Chiba and Kanagawa from 90 to 15 minutes, and also cut the travel time to the sea leisure area in the southern part of the Boso Peninsula from Tokyo and Kanagawa.
On the morning of 4th May, hubby and I left his home in Ichinomiya City at about 11 am and started back on our journey to Akita. My father-in-law and his wife also accompanied us as they wished to do sightseeing in the Kanto region in the evening and the next day. We all drove up to Yokohama City in Kanagawa prefecture by our car. It took us about 6.5 hours of car ride to reach Yokohama due to heavy traffic. We dropped my father-in-law and his wife off at a hotel in the city, and then continued our ride up to Chiba City in Chiba prefecture where we stayed at a hotel for the night. While going from Yokohama City to Chiba City, we drove along Tokyo Bay Aqua-Line Highway.
As I have written earlier here, Tokyo Bay Aqua-Line Highway is a bridge-tunnel combination roadway that connects Ukishima in Kawasaki City of Kanagawa prefecture with Nakashima in Kisarazu City of Chiba prefecture. The total length of this highway is 15.1 kilometers, which consists of a 9.6 kilometers long undersea shield tunnel and a 4.4 kilometers long bridge from an artificial island to the Kisarazu landing. We entered the highway from Kawasaki side, so we first entered the undersea tunnel. This tunnel is the world’s longest undersea road tunnel, and was constructed by shield tunneling. The tunnel excavation was carried out from August 1994 to August 1996. It was dug with a sealed shield machine in order to overcome the difficult conditions of high water pressure and a soft foundation. The machine was cylindrical, 14.14 meters in diameter, 13.5 meters in body length, and weighed 3.2 tons. Using eight such shield machines, the tunnel was constructed that runs at the depth of 60 meters under the surface of water. The segment lining structure of the tunnel is built in such a way that it safeguards the tunnel against large ground and hydraulic pressures, prevents seawater leakage, and provides protection from earthquakes. It should be mentioned that the tunnel diameter is the world's largest for an underwater shield tunnel used for roadway traffic. The cross-section diameter to the outside of the segment lining is 13.9 meters, and the inner diameter of 11.9 meters provides for two lanes of traffic in both directions. The exact ascending tunnel length is 9.576 kilometers and the descending tunnel length is 9.583 kilometers. We were happy to drive through the longest undersea road tunnel although it felt like driving through any other usual tunnel. We took several photos and also compiled a video of our drive though the tunnel. By the time we came outside the undersea tunnel portion of the highway, it had gotten dark and so we decided to visit Umihotaru Parking Area the next day. We drove across the bridge, and went to a hotel in Chiba City where we stayed for the night.
Entrance to the undersea tunnel portion of Tokyo Bay Aqua-Line Highway from Kawasaki side
Inside the tunnel we can see two traffic lanes. There is a second tunnel of the same size next to this one for cars driving in the opposite direction.
Our car navigation system indicating our position inside the tunnel
A compiled video of our drive through the undersea tunnel
On the morning of 5th May, we had breakfast and left the hotel at about 8 am. Again, we drove along Tokyo Bay Aqua-Line Highway. However this time we entered the highway from Kisarazu side, so first we drove across the bridge portion of the highway. At the entrance area of the bridge, we paid a toll fee of 2320 Yen for our normal sized car. While hubby was busy driving, I enjoyed the views around us and appreciated the architecture of the bridge. It is a 4.4 kilometers long arched bridge with four lanes of traffic, two in either direction. It is the longest road bridge across sea in Japan. It is a ten-span continuous steel box-girder bridge. The upper and lower part of the bridge were manufactured on land and transported by sea, and then set up with a crane and bogie ship loader. The bridge has several interesting design features. Firstly, the seams on the bridge are significantly reduced which allows for smooth passage of the cars and also reduces shaking. Secondly, the bridge is earthquake resistant to ensure the safety of the passengers. Thirdly, a variety of aerodynamic mitigation strategies are employed to suppress the wind induced vibration in the bridge. And fourthly, some portion of the bridge is raised like a hump which makes that portion higher than the rest of the bridge. In fact, the highest point of the bridge raises about 40 meters above sea level. This allows for 2000-ton class ferries to have easy access to pass under the bridge. It was a sunny day and we enjoyed driving across the bridge. We took several photos and also compiled a video of our drive across the bridge.
Toll gates at the entrance area of the bridge portion of Tokyo Bay Aqua-Line Highway on Kisarazu side
We are driving across the bridge. We can see four traffic lanes, two in either direction.
Driving across the bridge
Tokyo Bay and many high rise structures in the background as viewed from the bridge
Almost reached Umihotaru Parking area
A compiled video of our drive across the bridge
After driving for about five minutes across the bridge portion of Tokyo Bay Aqua-Line Highway, we reached a parking area called Umihotaru. Umihotaru, which literally means sea firefly, is an artificial island located at the bridge-tunnel crossover point of the highway. It is designed as a tourist attraction, and is a spectacular landmark jutting out from the waters of Tokyo Bay. This five-storied parking area measures 650 meters in length and 100 meters in width, and is designed in the shape of a cruise ship. Umihotaru Parking Area consists of parking lots on the 1st to 3rd floors, and many restaurants, shops, cafes and amusement facilities on the 4th and 5th floors. The fifth floor has an observation deck which is a popular scenic point for the tourists. Although it was a peak holiday season, we could easily find a parking spot at the first floor of the parking area. Parking at Umihotaru is free.
Umihotaru Parking Area designed like a cruise ship
Driving towards the parking area
The parking area and bus terminal
Roads leading to Umihotaru as viewed to our left side from the first floor of the parking area
Roads leading to Umihotaru as viewed to our right side from the first floor of the parking area
After parking our car, we used an escalator and reached the topmost fifth floor of Umihotaru Parking Area. There is an open-air observation deck on the top floor which commands a 360-degree panoramic view of Tokyo Bay. First we went to the southeast side of the observation deck, which faces Kisarazu City in Chiba prefecture. There were many visitors on the left side of the deck. So to avoid the crowd, initially we stood on the right side of the deck and got a wonderful view of the bridge portion of Tokyo Bay Aqua-Line Highway. The vast blue colored Tokyo Bay, the bridge, and the high rise structures of Chiba prefecture in the far background made for a stunning view. We saw a monument of a ship’s wheel as well as several sculptures of the head of tuna fish on the deck. It was a bright sunny day and we loved relaxing at the deck.
Panoramic view of Tokyo Bay and the bridge portion of Tokyo Bay Aqua-Line Highway clicked from the right side of the observation deck
View of a part of Umihotaru deck, bus terminal, and the bridge in the direction towards Kisarazu City
The bridge along with the bus terminal in the foreground
Enlarged view of the bridge where we can clearly see four traffic lanes, two in either direction
Hubby standing on the right side of the deck along with the bridge in the background
Hubby standing next to the monument of a ship’s wheel
Four sculptures of the head of tuna fish. Hubby is sitting on one of the heads and enjoying the views.
Afterwards we moved towards the left side of the southeast observation deck on the top floor of Umihotaru Parking Area. The bridge and the vast Tokyo Bay looked fantastic from this point also. In addition, we saw a monument of a marlin fish on the deck. After enjoying the views around us, we walked towards the northwest side of the observation deck.
View of a part of Umihotaru deck, bus terminal, and the bridge portion of Tokyo Bay Aqua-Line Highway clicked from the left side of the deck
Hubby standing on left side of the deck along with the bridge in the background
Hubby standing next to the monument of a marlin fish
North side of the observation deck
The northwest side of the observation deck faces the undersea tunnel portion of Tokyo Bay Aqua-Line Highway in the direction of Kawasaki City in Kanagawa prefecture. There were many visitors on this side of the deck also. We got a wonderful view of Tokyo Bay and the high rise structures of Kanagawa prefecture in the far background. The deck has various sculptures and decorations, which makes it very lively and appealing. We saw a beautiful blue colored monument which was created keeping in mind the bright blue bioluminescent light created by sea firefly (Umihotaru). There was holiday crowd all around us, and so we could not avoid them while clicking photos.
Panoramic view of the observation deck and Tokyo Bay in the direction towards Kawasaki City
I am standing at the observation deck
Hubby standing next to the bright blue colored monument at the deck
Next, we walked down several steps and reached near the edge of the northwest side observation deck. From the deck edge, we got a very clear view of where the artificial island Umihotaru ended. Standing at that point, we tried to imagine the undersea tunnel right in front of us under Tokyo Bay. Hubby tried to guess the location of the entrance to the undersea tunnel. We saw several ships and fishing boats in the bay. In addition, we could see several high rise structures in the hazy far background, one of which was Tokyo Skytree Tower standing tall to our right side.
Panoramic view of Tokyo Bay and the edge of Umihotaru artificial island in the direction towards Kawasaki City is seen in the photo. This edge of the island is probably where the entrance area of the undersea tunnel is located.
Edge of the artificial island to our left side
Edge of the artificial island right in front of us
Edge of the artificial island to our right side
Hubby standing near the edge of the artificial island
A fishing boat and a small ship in Tokyo Bay
Tokyo Skytree Tower is seen in the hazy far background. I modified the contrast and brightness of the photo to make the tower more noticeable.
Standing near the edge of the northwest side observation deck, we noticed two interesting structures. Firstly, we saw a distinctive white colored tower named Kaze-no-To located right in front of us in Tokyo Bay. The name of the tower means ‘the tower of wind’. The tower is located on a small artificial island. Air is supplied to the undersea tunnel by this white colored tower in the middle of the tunnel, by using the bay’s almost constant winds as a power source. Secondly, to our far left side near the edge of Umihotaru artificial island, we saw a huge wheel-like monument. It is the cutter face of one of the slurry shield machines used to drill the undersea tunnel. The drilling operation was done by rotating the cutter face. Eight slurry shield machines were used to drill tunnels from three points, that is, Ukishima in Kawasaki City, Kaze-no-To, and Umihotaru artificial island. The tunnels were then joined in the respective centers under the sea to form two tubes of 9.6 kilometers in length. The diameter of the shield machines is 14.14 meters, which makes these machines the world’s largest. Standing at the edge of the deck, we tried to imagine the undersea tunnel linking Umihotaru and Kaze-no-To.
Wheel-like monument located to the far left side near the edge of Umihotaru artificial island
Enlarged view of the cutter face
Afterwards, we turned around and climbed up the steps leading us back to the upper area of the northwest side observation deck. It was a bright sunny day and there were many people relaxing at the deck. In this area, we saw a monument of a globe as well as a monument of a pair of dolphins. We also saw several sculptures of turtles. It was fun to pose with these interesting monuments and sculptures.
Upper area of the northwest side observation deck as viewed from the lower edge of the deck
Monument of a globe
I am standing next to the monument of the globe
Monument of a pair of dolphins
I am standing next to the monument of the pair of dolphins
Hubby standing next to the sculpture of a turtle
At this point, we finished the tour of the open-air observation deck on the top floor of Umihotaru Parking Area. However, we again walked around this floor just to see various souvenir shops and restaurants. We saw several shops in the fourth floor also. Wonderful smell wafted out of some of the restaurants, but we did not eat anything as we had taken a heavy breakfast just a couple of hours earlier. I compiled a video of our walk along the fifth and the fourth floors of the parking area.
Portion of the fifth floor of Umihotaru Parking Area
Several banners in front of the restaurants (not seen) at the fifth floor promoting their food specialties
Going down the escalator to the fourth floor
Shops and other amenities at the fourth floor
A compiled video of our walk along the fifth and the fourth floors of the parking area
Afterwards, we left Umihotaru Parking Area and then drove through the undersea tunnel portion of Tokyo Bay Aqua-Line Highway. We entered the undersea road tunnel from Umihotaru, drove through the tunnel for about eight minutes, and then reached the exit area of the tunnel at Kawasaki City. Two traffic lanes inside the tunnel made our car ride rather smooth. I would like to mention that the previous day also we had driven through the tunnel, but that drive was through a different tube of the undersea tunnel with the traffic flow in the opposite direction.
Inside the tunnel we can see two traffic lanes. There is a second tunnel of the same size next to this one for cars driving in the opposite direction.
Hubby and I loved visiting Tokyo Bay Aqua-Line Highway and Umihotaru Parking area. In the afternoon, we visited Aizuwakamatsu Castle in Fukushima prefecture about which I will write in the next post.