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Grand Cayman is relatively well developed with a good infrastructure and a partially developed road network. New road links are proposed using roundabouts at the main intersections. The island has an extensive network of roads in and around George Town the capital of Grand Cayman; there are distinct rush hours in the morning and evening, typical peak periods rather like the UK, but there is an additional peak during the lunch period with congestion often developing on the network especially at some of the single lane roundabouts and the traffic signal junctions.
There is very little development of any alternative means of travel. Footways (sidewalks) are often not continuous and the weather is too hot to expect people to walk or cycle for significant distances. Occasional heavy downpours could drench walkers or cyclists. I looked in outline at possible ways to manage demand including car sharing, bus lanes, reducing parking availability in George Town, Park & Ride from an out of town development, covered cycle-way/footpaths and even light rail.
There may be a further possibility using an already partially developed canal system.
Roundabouts have been designed on the basis of the Australian model and there have been some driver problems with recognition of the roundabouts resulting in overshooting. Most of the roundabouts do not incorporate the white on blue turn left arrow that we use in the UK. So my first recommendation is to install these facing all approaches to their roundabouts. The placing of the chevrons that they have used was not always the best so we concentrated too on the exact locations of the new signs.
Many of the roundabouts were set up with single lane entries, but with additional passages on the left for left turning traffic - these were not generally free-flow; discussions with the original designer of the roundabouts build this way suggest a slight misunderstanding of the principles of modern roundabouts. He had hoped that drivers would "filter in" to these roundabouts to some extent - hence the single lane entry. Experience in the UK suggests that drivers are very poor at filtering in to anything except perhaps the free-flow situation on most motorway entry slip roads. So these designs have had relatively poor capacity with queues quick to form under any surge in traffic demand.
In just one case is a left turning lane virtually free-flow - the two exit lanes eventually have a merge-in-turn system; mostly drivers have to give way to re-join the traffic stream exiting the roundabout, often at a most uncomfortable angle. Many vehicles on the island are left-hand-drive so this has proved difficult especially for drivers of trucks. I have recommended closing the worst of these and in most cases adding at least one additional lane to each of the main roundabout entries. Amendments have been done and the new arrangements are reported to be working well.
These images show typical problems that we have had and continue to have when the roundabout is not clearly visible on approach. In this instance the chevrons are used in isolation and are incorrectly located:
We examined some sites locally for prospective retrofit to mini-roundabout and there is a very suitable site near the airport at a right-hand shoulder junction known as "Malfunction Junction"! This site is capable of easy conversion to a very small solid centre roundabout and will pave the way for the introduction of mini-roundabouts shortly thereafter. In the centre of George Town two mini-roundabouts have now been introduced where a new link road will provide a local alternative route to the main road along the coast. It is proposed to reduce traffic on this latter route and even pedestrianise it at peak times of visitor traffic when cruise ships come to George Town (most days between about 10am-4pm).
A future scheme is proposed where a new harbour jetty is to be provided for the cruise ships. The T-junction is currently controlled by signals. My Millennium Vision design attracted considerable interest and is now being considered the best way forward for this junction which is expected to handle very large numbers of pedestrians. See crossroads design on the Millennium Vision page.
Access to the new jetty will not now line up with this junction. Judging by conditions when we landed here recently (there were SEVEN cruise ships in on the same day!) it will be very difficult to control traffic sensibly.
My special thanks to Mark Scotland, Peter Ogden and Edward Howard for inviting me to help with their traffic problems. I look forward to a return visit to install the schemes discussed and to make sure that the larger roundabouts work a little better. The return visit came rather unexpectedly on a Caribbean cruise - hence the updates...
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Clive Sawers - May 2007