Remove dead link thanks to CRAN checks

Author: Robinlovelace

Diff for: vignettes/stplanr-paper.Rmd

@@ -689,7 +689,8 @@ Furthermore, with the development of online application frameworks such as **shi
 
 This paper has demonstrated the great potential for R to be used for transport planning. R's flexibility, powerful GIS capabilities \citep{bivand_applied_2013} and free accessibility makes it well-suited to the needs of transport planners and researchers, especially those wanting to avoid the high costs of market-leading products. Rather than 'reinvent the wheel' (e.g. with a new class system), **stplanr** builds on existing packages and \CRANpkg{sp} classes to work with common transport data formats.
 
-It is useful to see **stplanr**, and R for transport planning in general, as an addition tool in the transport planner's cabinet. It can be understood as one part of a wider movement that is making transport planning a more open and democratic process. Other developments in this movement include the increasing availability of open data \citep{naumova_building_2016} and the rise of open source products for transport modelling, such as [SUMO](https://www.dlr.de/ts/en/desktopdefault.aspx/tabid-9883/16931_read-41000/), [MATSim](https://www.matsim.org/) and [MITSIMLAB](https://www.its.mit.edu/software/mitsimlab) \citep{saidallah_comparative_2016}. **stplanr**, with its focus on GIS operations rather than microscopic vehicle-level behaviour, can complement such software and help make better use of new open data sources.
+It is useful to see **stplanr**, and R for transport planning in general, as an addition tool in the transport planner's cabinet. It can be understood as one part of a wider movement that is making transport planning a more open and democratic process. Other developments in this movement include the increasing availability of open data \citep{naumova_building_2016} and the rise of open source products for transport modelling, such as [SUMO](https://www.dlr.de/ts/en/desktopdefault.aspx/tabid-9883/16931_read-41000/), [MATSim](https://www.matsim.org/) and MITSIMLAB \citep{saidallah_comparative_2016}.
+**stplanr**, with its focus on GIS operations rather than microscopic vehicle-level behaviour, can complement such software and help make better use of new open data sources.
 
 Because transport planning is an inherently spatial activity, **stplanr** occupies an important niche in the transport planning software landscape, with its focus on spatial transport data. There is great potential for development of **stplanr** in many directions.
 Desirable developments include the additional of functions for modelling modal split, for examample with functions to create commonly distance decay curves which are commonly found in active travel research \citep{martinez_new_2013} and improving the computational efficiency of existing functions to make the methods more scalable for large databases.