and increased 30 m for each one degree decrease in ∆. According to both AASHTO and Iraqi Highway Design Manuals, the following are the general design controls for horizontal alignment: 1- Alignment is as smooth as possible 2- When using compound curve R2 must not be more than 1.5R1 3- Avoid using broken-back curves 4- Avoid using reverse curves 5- Curves should be 150 m long for ∆ = 5 deg. There are four common types of horizontal circular curves simple, compound, broken-back, and reversed.
A full station is defined as 100m or 1000m. Distance along a horizontal alignment is measured in terms of stations. Tangents are the straight segments of horizontal roads that can be defined in terms of their directions and lengths.
Horizontal alignment of roads usually comprises of tangent distances, that are connected by very gradual circular curves, that may be complemented by transitional spiral curves, to accommodate a given design speed with comfort and safety. Vertical alignment and cross- section elements will be discussed in the next lectures. This lecture discusses Horizontal Alignment of highways only. The third component is the cross-section of the highway which includes elements such as the travelled lanes, shoulders, curbs, medians, and others. Secondly, vertical alignment of a highway deals with its shape in profile. Firstly, horizontal alignment of a highway defines its location and orientation in plan view. The design of the alignment depends primarily on the design speed selected for the highway. Geometric design of a highway includes three major components horizontal alignment, vertical alignment as well as the cross-sectional elements.
The information listed in this lecture is mainly taken from the Policy on Geometric Design of Highways and Streets (AASHTO, 2011), Iraqi Highway Design Manual (SORB, 2005) and Traffic and Highway Engineering (Garber and Hoel, 2009). B- Circular curves (Simple, Compound, Broken-back and Reversed). Highway Horizontal Alignment In this lecture -Highway Horizontal Alignment.
Let's take a look at how to do this simply and make our documents look polished using "tab stops." When you are typing in Word and press the "tab" button, you will usually see a noticeable amount of space inserted before the next thing you type. One way is to type everything and play around with inserting extra spaces until it all "looks good." But this is an inefficient and imprecise process. But what if you wanted to use more than one type of alignment on the same line? For example, in college many of us had to write paper and label it with our name, the date, and the class name. You may already know how to align text on the