Line-based
Individual lines can have a regular schedule, even without connections to other lines. Nevertheless, it could be necessary to co-ordinate the schedules of different modes of transport if links are made between them, such as at the terminal stop of a tram network if a journey can be continued by bus, so that passengers do not have to wait long at transfer point until the next service arrives. Clock-face timetables can be attractive even if services provide no connections to other public transport because they allow a continuous use of vehicles and personnel. Line-bound regular timetables are especially useful for lines with high service frequencies. If vehicles with the same destination follow each other in short intervals, transfer times are short even if there are delays. However, if the service intervals are 20 minutes or longer, it is important for schedules on each line to be officially co-ordinated. One simple way of doing that is to shift the departure times of one of the lines to match the other.Network-based
An integrated schedule is a clock-face schedule that covers not individual lines but all public transport services in a given area. A characteristic of integrated clock-face timetables is that there is more than one central hub. A hub-and-spoke approach is then applied to the whole transport network. Having several services meet at hubs where all of them arrive and leave at the same time is the most effective way of connecting multiple routes and modes. The goal is to reduce transfer times to a few minutes, with a default time of no more than five minutes. In actual operation, the time span can be longer because of services running early or late, high passenger volume (such as rush hour), or the need to assist passengers with disabilities. Efficient operation is even more essential than normal with integrated clock-face timetabling. If the policy is to hold connecting services to ensure a connection with a late-running service, waiting times at interchange stops can become unattractive, and other services will run late as a consequence. Examples of such networks are often night and city bus networks. The connections might be optimized only within the network but not for transfers to rail or intercity bus lines. Such concepts need purpose-built stations, which can handle high passenger volumes. The space constraints within cities can be a reason to use other concepts. An integrated regular timetable with half-hourly or hourly headways requires routes on which a service takes 28 or 58 minutes to make it from one hub to another. A service that takes 40 minutes would be bad because passengers and vehicles have to wait uselessly for their connections (unless the timetables at the different hubs are offset from each other to compensate, which is only practical for networks with very few hubs), and it generates nearly the same cost as a route that takes 58 minutes because vehicles and personnel cannot be used during the remaining 20 minutes. Therefore, when an integrated timetable is introduced running times might be cut or extended to meet the ideal duration.Emergence of integrated timetables
The first integrated regular timetables were developed for railways. After the successful introduction of a line-bound regular timetable on one line in Switzerland in 1968, the development continued in the Netherlands. In 1970 and 1971, theSwitzerland
Services on the Swiss railway network are integrated with one another and with other forms of public transport. Unlike its larger European neighbors, compact Switzerland has not developed a comprehensive high-speed rail network, with the running speed on its few stretches of relatively high-speed line being . Instead, the priority is not so much the speeding up of trains between cities but the reduction of connection times throughout the nodal system. Swiss Federal Railways have adapted their infrastructure in such a way that journey times on main lines between hubs are multiples of 30 minutes so that on the hour or half-hour, all trains stand in the main stations at the same time, thus minimising connection times. Indeed, the above-mentioned Mattstetten–Rothrist line reduces journey times from Bern to Zurich from 72 minutes to 56 minutes in keeping with the clock-face scheduling. The Swiss approach is sometimes called "as fast as necessary" with a schedule being written mandating specific travel times and infrastructure later upgraded in line with the proposed schedule. This was the main idea behind the Bahn 2000 project and has also been used for the passenger travel through the NRLA tunnels. However, on some single tracked lines the timetables may be 30/30 or 60/60 minutes, with the actual timetables being asymmetrical (such as 20/40 minutes), because passing loops are not positioned ideally, or alternate connections at either ends have to be reached.Germany
Since 1990, most of the states of Germany have introduced integrated timetables, running hourly or every two hours, for short-distance public transport such as Allgäu-Schwaben-Takt (commencing in 1993), Rheinland-Pfalz-Takt (1994) and NRW-Takt (1998). Transport associations have introduced regular timetables with base frequencies of 20 or 30 minutes, which are partially changed to 10 or 5 or even 15 or 7.5 minutes when locations are served by overlapping multiple lines. In some areas, local buses are also integrated, such as RegioTakt in Northrhine-Westphalia and in parts ofReferences
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