A concurrency in a road network is an instance of one physical roadway bearing two or more different route numbers. When two roadways share the same right-of-way, it is sometimes called commons. Other terminology for a concurrency includes overlap, duplex, multiplex, dual routing or triple routing. Concurrent numbering can become common in jurisdictions that allow it. Where multiple routes must pass between a single mountain crossing or over a bridge, or through a major city, it is economically and advantageous for them all to be accommodated on a single physical roadway. In some jurisdictions, concurrent numbering is avoided by posting only one route number on highway signs. However, any route that becomes unsigned in the middle of the concurrency will still be signed on most maps and road atlases. Most concurrencies are a combination of at least two route numbers on the same physical roadway; this is practically advantageous as well as economically advantageous. Some countries allow for concurrencies to occur, others do not allow it to happen.

In those nations which do permit concurrencies, it can become common. In these countries, there are a variety of concurrences. An example of this is the concurrency of Interstate 70 and I-76 on the Pennsylvania Turnpike in western Pennsylvania. I-70 merges with the Pennsylvania Turnpike so the route number can continue east into Maryland. A triple Interstate concurrency is found in Wisconsin along the five-mile section of I-41, I-43, I-894 in Milwaukee, Wisconsin; the concurrency of I-41 and I-43 on this roadway is an example of a wrong-way concurrency. The longest Interstate highway concurrency is I-90 for 265 miles across Indiana and Ohio. There are examples of eight-way concurrencies: I-465 around Indianapolis and Georgia State Route 10 Loop around downtown Athens, Georgia. Portions of the 53-mile I-465 overlap with I-74, US Highway 31, US 36, US 40, US 52, US 421, State Road 37 and SR 67—a total of eight other routes. Seven of the eight other designations overlap between exits 46 and 47 to create an eight-way concurrency.

In the United States, concurrencies are marked by placing signs for both routes on the same or adjacent posts. The federal Manual on Uniform Traffic Control Devices prescribes that when mounting these adjacent signs together that the numbers will be arranged vertically or horizontally in order of precedence; the order to be used is Interstate Highways, U. S. Highways, state highways, county roads, within each class by increasing numerical value. Several states do not have any concurrencies, instead ending routes on each side of one. There are several circumstances. One example occurs along the Oklahoma–Arkansas state line. At the northern end of this border Oklahoma State Highway 20 runs concurrently with Arkansas Highway 43 and the two highways run north–south along the boundary. Concurrencies are found in Canada. British Columbia Highway 5 continues east for 12 kilometres concurrently with Highway 1 and Highway 97, through Kamloops; this stretch of road, which carries Highway 97 south and Highway 5 north on the same lanes, is the only wrong-way concurrency in British Columbia.

In Ontario, the Queen Elizabeth Way and Highway 403 run concurrently between Burlington and Oakville, forming the province's only concurrency between two 400-series highways. The concurrency was not in the original plan which intended for both the QEW and Highway 403 to run parallel to each other, as the Hamilton–Brantford and Mississauga sections of Highway 403 were planned to be linked up along the corridor now occupied by Highway 407, it was planned for the Mississauga section of Highway 403 would be renumbered as Highway 410 but this never came to pass. Highway 403 was signed concurrently along the Queen Elizabeth Way in 2002, remedying the discontinuity to avoid confusing drivers that wanted to travel between the two segments without using the toll Highway 407. Nonetheless, many surface street signs referring to that section of freeway with the QEW/Highway 403 concurrency still only use the highway's original designation of QEW, although the MTO has updated route markers on the QEW to reflect the concurrency.

In the United Kingdom, routes do not run concurrently with others. Where this would occur, the roadway takes the number of only one of the routes, while the other routes are considered to have a gap and are signed in brackets. An example is the meeting of the M60 and the M62 northwest of Manchester: the motorways coincide for the seven miles between junctions 12 and 18 but the motorway between those points is only designated as the M60. European route numbers as designated by UNECE may have concurrencies, but since the E-route numbers are unsigned and unused in the UK, the existence of these concurrencies is purely theoretical. In Sweden and Denmark, the most important highways use only the European route numbers that have cardinal directions. In Sweden the E6 and E20 run concurrently for 280 kilometres. In Denmar

The total acid number is a measurement of acidity, determined by the amount of potassium hydroxide in milligrams, needed to neutralize the acids in one gram of oil. It is an important quality measurement of crude oil; the TAN value indicates to the crude oil refinery the potential of corrosion problems. It is the naphthenic acids in the crude oil that cause corrosion problems; this type of corrosion is referred to as naphthenic acid corrosion. TAN values may be useful in other industries where oils are used as lubricants to determine oxidation and the subsequent corrosion risk to machinery. TAN value can be deduced by various methods, including Potentiometric titration: The sample is dissolved in toluene and propanol with a little water and titrated with alcoholic potassium hydroxide. A glass electrode and reference electrode is immersed in the sample and connected to a voltmeter/potentiometer; the meter reading is plotted against the volume of titrant. The end point is taken at the distinct inflection of the resulting titration curve corresponding to the basic buffer solution.

Color indicating titration: An appropriate pH color indicator e.g. phenolphthalein, is used. Titrant is added to the sample by means of a burette; the volume of titrant used to cause a permanent color change in the sample is recorded and used to calculate the TAN value. Spectroscopic methods: as with many chemical parameters, spectroscopy can be used to make fast, accurate measurements once calibrated by a reference method. Mid and near infrared spectroscopy are most used for this purpose. Spectroscopic methods are valuable as they can be used to measure a number of other parameters and do away with the need for wet chemistry. Total base number

Sant'Antonio Abate is a Baroque-style, Roman Catholic church located on Via Bella at Piazzetta don Galliano, in Acqui Terme, Province of Alessandria, region of Piedmont, Italy. The church was commissioned in 1608 by the Barnabite order, dedicated to Saint Paul and allied to the local convent of the same name, it was rebuilt in 1701. In 1812, the church was conferred to the custody of the Confraternity of San'Antonio; the church houses Rococo wooden choir stalls and pulpit. The church houses four 18th-century canvases depicting Saints Ambrose, Agatha and John of Nepomuk, which belonged to the oratory; the wooden statue of the Virgin dates to the 18th century. The organ was built in 1837 by Giosuè Agati of Pistoia