the low level of Cologne Messe/Deutz railway station (tracks 11 and 12) from the west (Aachen) through Cologne main station and over the Hohenzollern Bridge or from the north to the main station and then reversing to re-cross the Hohenzollern Bridge from the north over the Hohenzollern Bridge to the main station and continuing around the western bypass of central Cologne and over the Cologne south bridge The first two routes allow trains to run via Cologne–Bonn airport loop line, rejoining the main route at Cologne-Porz-Wahn. The high-speed line's dedicated track begins in Cologne-Porz and are located between the Sieg Railway and the line from Gremberg yard and the Cologne south bridge, which, in effect, becomes the Right Rhine line when it separates at Troisdorf. Between Porz and Troisdorf there are six parallel lines and the speed limit on the HSL is . At Troisdorf the HSL runs through a tunnel under connecting lines that allow passenger trains running on the Sieg line to transfer to the Right Rhine line and freight trains on the freight lines to transfer to the Sieg line (and vice versa for northbound trains). In Troisdorf the Right Rhine line leaves the high-speed line and runs through Bonn-Beuel towards Koblenz. The HSL follows the Siegstrecke to the rebuilt Siegburg/Bonn station and then heads south to run through the Siegauen Tunnel under the Sieg. At that very point it joins the A3, which it parallels south bound towards Frankfurt Airport. Between the Siegauen Tunnel and the Main Bridge (near Frankfurt) the speed limit is and from there to the airport station trains run at . In the Wiesbaden suburb of Breckenheim a double line connects to Wiesbaden, partly next to the A66 and then next to the Ländches Railway. Trains run into the Wiesbaden terminal station and can then reverse out to go to Mainz and Mannheim. The Wiesbaden branch has a maximum speed of about . Construction on the approach to Cologne Work is being carried out to create separate tracks for the high-speed line through the heavily used Cologne rail junction from its provisional connection to the conventional line at Köln Steinstraße, where trains are limited to through the points. The line is being extended to Cologne-Mülheim station through Cologne Messe/Deutz railway station (low level). This work was intended to be part of the original high-speed line project, but was dropped to reduce costs.