Construction Change Directive: Fill & Download for Free

1. This is Seismic Isolation, a means of protecting the structure against earthquake.How?It detaches the structure from the ground so that earthquake motions are not directly transmitted.2. This is an Expansion Joint -Expansion joints are provided along the transverse direction to allow movement (expansion/contraction) of the construction materials without inducing stresses due to changes in temperature or other reasons.Of course they weren't made to annoy you while driving!3. The ratio of the length to width of a room is generally between 1.5 to 2.1 (India) so that we don't feel like living in a box or tunnel!4. This is called Mid-Landing -This allows the stairs to change direction and the user to rest a little.The minimum height of each step (rise) should be 15 cm and width (tread) 25 cm. (India)By the way, each stairway is a flight!5. The outer edge of road at the horizontal curve is raised above the inner edge, this is Super ElevationIt reduces the effect of centrifugal force on the running wheels. If this is not provided the entire centripetal force is provided by the friction between the vehicle's tires and the roadway, thus reducing speed.6. And this is a Theodolite! :)It is used to measure distances and angles in horizontal and vertical planes.

There were essentially three big issuesLack of coordination. There were highways that went long distances maintained partly by the U.S. government, like Route 66. However, in many cases, if you were travelling long distances by car, even if you had a map, there was no clearly defined route. Most major highways passed through the center of towns and cities and would suddenly change direction without really good markings. It wasn’t uncommon for you to drive for miles before realizing you were on the wrong road and you would have to backtrack. Even Route 66, which was fairly well marked, was re-routed constantly to try to either provide a shorter route in places or to bypass congested areas.Lack of maintenance. Many of the roads couldn’t be used full time. Many were unpaved. Some weren’t maintained in winter (a particular problem getting through the Rockies). Some regularly flooded in spring and you were still expected to drive through water to get through the other side.Lack of standards. Many long roads were narrow, essentially built about 24 feet wide with no shoulders or guardrails. They often contained tight turns. Many had severe grades, and not just in mountainous states, even in ones with rolling hills.So, imagine negotiating an unpaved road 24 feet wide with no shoulders, guardrails or center line, in rainy season, with few markings, hairpin curves and grades of 5%. You can still find lots of roads in the United States like that. But not on an interstate.

When I studied road construction at University, many many years ago, the professor told us this story:In the old times, when a road had to be built up a hill, the team of prospector would lead a donkey or a mule up the incline. The donkey would not go straight up along the shortest route, but would instinctively follow a path with a moderate incline, or grade, very similar to the maximum grade considered safe for roads (8 to 10%).The prospectors would hammer stakes in the ground after the donkey and then measure the position of the stakes, draw all the points on a map and start drawing the road profile after joining the dots.When the prospectors felt that the donkey had gone too far from the desired direction, or when an obstacle was met, they would turn the donkey around and it would continue climbing in the opposite direction with the same incline. The point where the donkey changed direction would be the location of a hairpin turn.Image from the internet: this incredibly winding road is somewhere on the Andes range in South AmericaA powerful car with adequate gear ratios (and adequate grip) can go up a very steep incline but a loaded freight vehicle or a bus full of passengers cannot. As many have pointed out in their answers, going downhill on a very steep incline can be extremely dangerous.An incline, or grade of 8% is considered the limit for a major road. For short distances, 10% 15% and even 20% grades can be considered acceptable on minor roads, but must be accompanied by adequate signage.Some very exceptional grades exist on some mountain roads, but I would not want to travel with a truck on such a road:EDIT: Note that “grade” and “angle” of a slope are two different measures since “grade” indicates how much one climbs given a certain distance travelled in horizontal.For example, if you travel 1000 m (1 km) in a horizontal direction and at the same time climb 100 m, then the grade would be:100 m/ 1000 m = 1/10 or 10%One good thing of expressing the rate of climb this way is that it is independent from the unit of distance that you use, as long as it is the same for horizontal and vertical distances. If you measure horizontal distance and climb in miles you will reach the same result as when using metric units (but not if you measure distance in miles and climb in feet!)A grade of 10% corresponds to an angle of about 6° and a grade of 50% corresponds to an angle of 27°. A slope with an angle of 45° would have a grade of 100%Those who are keen on trigonometry, or who have recollections of it from school, will recognize that the “grade” is equivalent to the “tangent” of an angle, apart from the unit, which for the trigonometrical tangent is a pure number, while grades are expressed in percent (%) or per-thousand (used in railway engineering, where grades are very small) to get rid of decimals.