Editing Diamond interchange (section)

=== Dogbone ===
[[File:N.C. 108 roundabout.JPG|thumb|right|A "raindrop" of a dogbone interchange along [[Interstate 26 in North Carolina|Interstate 26]] in [[Columbus, North Carolina]], United States<br />{{coord|35|14|43.7|N|82|12|20.2|W}}]]

A variation of the dumbbell interchange, often called a '''dogbone interchange''' (due to its aerial resemblance to a real or toy [[dog toy#Bones|dog bone]]), and sometimes also called a ''double roundabout interchange'',<ref name="FHWA 9"/> occurs when the roundabouts do not form a complete circle but instead have a "[[wiktionary:raindrop|raindrop]]" or "[[wiktionary:teardrop|teardrop]]" shape. These two [[roundabout#Raindrop roundabouts|raindrop roundabouts]] are fused together, forming a single "squashed" roundabout.

This configuration reduces conflicts between vehicles entering the raindrop roundabouts from the ramps, reducing queueing and delays, compared with the dumbbell interchange. Direct U-turns are not possible, although the movement can be made by circulating around both raindrop roundabouts.<ref name="ATTAP"/> An example of a dogbone interchange in the United States is located on [[Interstate 70]] in [[Avon, Colorado]], United States;<ref>{{google maps|url=https://maps.google.com/maps?f=q&source=s_q&sll=37.0625,-95.677068&sspn=33.901528,79.101563&ll=39.637253,-106.520707&spn=0.001913,0.006866&t=k&z=18 |title=Teardrop roundabout in Avon, CO}}</ref> more compact examples, which show less of the characteristic "dog bone" shape, are located along [[Keystone Parkway]] in [[Carmel, Indiana]], United States. Several interchanges similar to those along Keystone Parkway are being built along the new [[U.S. Route 31 in Indiana|US 31]] freeway under construction in northern Indiana.<ref>{{ cite web | title = The New US 31 Hamilton County: Frequently Asked Questions | url = http://us31hamiltoncounty.in.gov/faqs/ | date = March 2015 | publisher = [[Hamilton County, Indiana|Hamilton County]], Indiana | access-date = December 3, 2015 }}</ref>

There are some hybrid interchanges of dumbbell and dogbone having one raindrop and one full roundabout. This is made when the roundabout intersects more roads than the cross street and ramps. Some examples are at exit 38 of the [[N7 road (Netherlands)|N7 road]] in [[Groningen]], Netherlands (at {{coord|53.21462|N|6.602509|E}}); and [[Ennis Avenue]] ([[Highway 1 (Australia)|National Route 1]]) at [[Safety Bay Road]] ([[list of road routes in Western Australia#18|State Route 18]] / [[Tourist Drive 202 (Western Australia)|Tourist Drive 202]]) on the border of the suburbs of [[Waikiki, Western Australia|Waikiki]] and [[Warnbro, Western Australia|Warnbro]] in the [[City of Rockingham]], [[Western Australia]] (at {{coord|32.32486|S|115.76704|E}}).

A '''tennis ball interchange''' resembles a dogbone interchange, with the difference being that right turning movements (in a country where traffic [[right- and left-hand traffic|drives on the left]]) cut through the roundabouts like a regular diamond interchange instead of going around the roundabout. Such a design is found in [[Perth]], Western Australia, between [[Roe Highway]] ([[List of road routes in Western Australia#3|State Route 3]]) and Berkshire Road (at {{coord|31.96945|S|116.00107|E}}).<ref>{{cite web|title=Roe Highway / Berkshire Road Interchange|url=http://gatewaywa.com.au/assets/Uploads/Roe-Highway-Berkshire-Road-Factsheet.pdf|date=April 2015|website=Gateway WA|publisher=[[Gateway WA]]|access-date=26 September 2015|archive-url=https://web.archive.org/web/20150926083217/http://gatewaywa.com.au/assets/Uploads/0413-roe-hwy.berkshire-rd-factsheet.web.pdf|archive-date=September 26, 2015 |url-status=live}}</ref>