No Entry

Synonyms / Other Terms Used

Do Not Enter, No Admittance, Keep Out, No Trespassing

Category

Safety, Regulations, General Information

Message / Function

To signify that entry is prohibited or restricted

	Source	Description
	Dreyfuss	Upraised hand, thumb on the right
	AfixGraf	Upraised hand, thumb on the left, inside red circle
	CPI	Upraised hand, thumb on the left, crossed out with slash, inside red circle
	Dreyfuss	Upraised hand with exclamation mark superimposed, inside red circle
	DURABLE	Upraised hand plus text 'STOP', inside red circle
	NIRS Israel	Red octagonal sign with white border, showing upraised hand
	CLP	Perspective view of person reaching out an upraised hand
	ISO 1975	Perspective view of person reaching out an upraised hand
	DIN 4844-2	Perspective view of person reaching out an upraised hand
	Avery	Person showing large upraised hand
	Icograda	Direction arrow pointing towards rectangle indicating room with door closed
	Icograda	Direction arrow pointing towards opening of circular enclosure and X inside
	Icograda	Direction arrow pointing into opening of rectangular enclosure, crossed out with X
	UN 1968	Red circle, white background, arrow pointing upwards crossed out with slash
	BTP	Human figure walking touching partially opened door, crossed out with slash
	O'72	Front view of human figure walking, crossed out with horizontal bar
	UIC	Human figure walking right hand, crossed out with slash
	ISO 1975	Human figure walking left hand, crossed out with slash
	ISO 7010	Human figure walking left hand, crossed out with slash
	Unknown	Human figure walking right hand, crossed out with slash
	WO'72	Front view of human figure standing, crossed out with X
	JIS	Front view of human figure standing, crossed out with slash
	ANSI Z535.2	Front view of human figure standing, crossed out with slash
	Olgyay	Front view of human figure standing and arms outstreched, crossed out with slash
	ÖNORM S 4610	Front view of human figure standing, arms streched out
	ÖNORM S 4610	Front view of human figure standing, arms streched out, inside red circle
	ÖBB 2007	Front view of human figure standing, arms extended horizontally
	Dreyfuss	Front view of human figure standing, arms extended horizontally
	Dreyfuss	Front view of human figure standing, arms extended horizontally, white horizontal bar inside red disk behind
	UN 1968	White horizontal bar inside red disk
	AIGA	White horizontal bar inside red disk
	TA	White horizontal bar inside red disk
	StVO D	White horizontal bar inside red disk
	STA	Yellow horizontal bar inside red disk
	UN 1968	Red octagonal sign with text 'STOP'
	StVO D	Red octagonal sign with text 'STOP'
	Dandiwal	Red octagonal STOP sign in Punjabi language
	UN 1968	Red circle with a red inverted triangle with white background, and text 'STOP'

Besides the general messages above, additional variants related to specific dangers are in use, too.

	Source	Description
	ÖNORM S 4611	Upraised hand with text 'STOP' superimposed behind a mountain, text 'Danger of avalanches' below
	RVS 05.06.31	Upraised hand with UN 1968 traffic sign No Entry superimposed, text 'STOP' above and 'FALSCH' (WRONG) below
	W-RSN	Upraised hand with UN 1968 traffic sign No Entry superimposed, text 'STOPP' above and 'SNU' (TURN) below

Test results

Studies from several countries present research covering many pictogram variants found:

To identify the best variants before testing for comprehensibility, Easterby & Graydon (1981 a) inspected more than 60 pictogram variants with the message No Entry on basis of two Appropriateness Ranking Tests. This study brought about the following results:

The ISO 1975 variant showing a combination of a walking human figure with a slash inside a circle and a similar design were judged as most appropriate.
The variations of symbol C, 1^a from the 20. Convention on Road Signs and Signals (UN 1968), a white horizontal bar inside a red disk, appeared in scaled ranks 10 to 23.
Upraised hands / hands with fingers upwards in all variations appeared in scaled ranks on position 24 (a version inside a circle) or further behind. These therefore were seen as less appropriate. The only exception was the variant labeled ISO 1975, where the hand is the dominant part of a close-up view of a person, on position six.
All pictogram variants displaying a human figure with arms streched out horizontally were placed in rear ranking positions with the best one on scaled rank 33. So these were judged as almost least appropriate.
Pictograms showing just a crossed out front or back view of a man standing are spread over the whole range of variants tested.

Data from six countries collected in a follow-up Comprehension Test (Easterby & Graydon, 1981 b) is available for three variants:

Easterby & Graydon, 1981 b
	TA	ISO 1975	ISO 1975
Percentage correct, strict scoring	37.5 %	8.3 %	14.1 %
Percentage correct, lenient scoring	53.0 %	81.3 %	83.1 %

Applying a strict scoring scheme, the abstract version from Tokyo Airport (TA) derived from the Convention on Road Signs and Signals performed best with 37.5 % correct responses. The other two just elicited 8.3 % and 14.1 % correct responses, values not realistic and induced due to problems induced by local translation and central scoring procedures. Regarding more lenient scoring where responses like 'Stop', 'No trespassing', 'Do not pass', but also 'No men admitted' etc. were judged as correct, the TA symbol reached 53 % correct responses. The two ISO 1975 variants reached 81.3 % and 83.1 % correct responses and performed much better under these scoring conditions.

Collins, Lerner & Pierman, 1982
	UN 1968, TA	CLP	ANSI Z535
Labels used by the authors	A	B	C
Percentage correct, strict scoring	20.4 %	13.8 %	74.4 %
Percentage correct, lenient scoring	30.6 %	85.0 %	76.7 %

Collins, Lerner & Pierman (1982) examined three variants in an industrial setting. Among industrial workers and using a strict scoring scheme, the sign showing a white horizontal bar inside red disk reached 20.4 % correct responses, the pictogram labeled B 13.8 % and C 74.4 %. Applying more lenient scoring the potential of the variants tested becomes more obvious with 30.6 %, 85.0 %, and 76.7 % correct responses. The authors give more information on details: 'Although image B does not communicate the strict message of "no entry” well at all, it does communicate the idea of "stop” to 72 percent of those tested (industrial or naive). Image C indicates "no entry" to about 75 percent of those tested and "no standing" to another 12 percent' (page 80).

Silver et al., 1995
	DIN 4844-2	Gen	UN 1968, TA	Gen	StVO D
Percentage correct with context	24 %	42 %	37 %	26 %	63 %
Percentage correct without context	33 %	44 %	22 %	30 %	5 %

In the paper Comprehension and Perceived Quality of Warning Pictorials (Silver et al., 1995) five variants for 'Keep Out' were studied, and answers like 'Do not enter', 'Stay away', etc. were counted as correct. As shown in the table above, pictorials were tested under two conditions: with context and without context information. And in addition each respondent had to rate each pictorial how well the appropriate message was conveyed. Variant X revealed highest comprehension rate in the without context condition, while the STOP sign showed the best score with context. Concerning message quality ratings, the DIN 4844-2 variant was best, followed by the STOP sign. The UN 1968 variant reveived the lowest quality rating.

Olgyay, 1996
	Olgyay	ANSI Z535	UN 1968, TA
Percentage correct	88 %	67 %	21 %

In a report detailing her research to improve the design of the ANSI Z535 safety symbols, Nora Olgyay (1996) presented background information and Comprehension Test data concerning the pictograms labeled ANSI Z535 and Olgyay: 'To clarify the NO ENTRANCE safety message, SEGD's person has outstreched arms to imply movement. The recrafting of this graphic detail improved its comprehension score and reduced the incidence of misreadings previously recorded for its Z535 counterpart as 'No Men' by more than half.' (Olgyay 1996, page 16). Correct responses registered in this study: 67 % for the ANSI Z535 sign vs. 88 % for the recrafted version.

Discussion

The examples shown above are only a small selection from the wide range of pictograms and symbols for the referent No Entry and the related terms Restricted Access, No Trespassing, etc. that can be found in publications and guiding systems worldwide. There are several general concepts and a multitude of visualizations. It seems there is no real single stereotype to express this message. In such a case often no satisfying solution with good comprehensibility can be determined. Moreover some of the variants in use are contradicting each other and therefore increasing the complexity of this situation.

Signs with a human figure walking, crossed out with a slash, as for example shown in the Vienna Convention on Road Signs and Signals, performed best in two of the test/scoring conditions presented. But it has to be regarded that this symbol is defined in several standards like ISO 7010, ÖNORM S 4611, etc. to prohibit use by pedestrians, so users with specific equipment like skis may pass where this symbol is shown.

As data for the pictogram variant presented by Olgyay - a front view of human figure standing and arms outstreched - reveals good comprehensibility despite the fact that the slash may be misleading, it might make sense to study a variant like the one labelled ÖBB in the table above. A similar older UIC variant reached 65.5 % correct answers in a Comprehension Test conducted in Austria (Brugger, 1996), when a rather general context information 'in a railway station' was provided.

Pictograms displaying an upraised hand exist in many variations, most with a red circle implying prohibition, some even with an additional slash. This slash in most cases is interpreted as negation of the message signified by the pictogram, but in case of these variants it seems to be intended as reenforcement of the prohibition. This possibly is a main reason for the huge differences regarding correct comprehension. The same can be assumed for the perspective view of person reaching out an upraised hand. The versions without slash probably convey the intended message quite well, but it should be kept in mind, that in some cultures presenting an upraised hand may be an insulting gesture (Christian, 2017).

The UN 1968 variant showing a white horizontal bar inside red disk is an abstract traffic sign that has to be learned and reaches much better comprehension among drivers. Comprehension levels for this symbol in articles related to traffic signs are usually above 75 % (Berrio et.al., 2023) compared to 20 % to 53 % in the studies mentioned above.

A considerable amount of responses for the STOP sign, when presented without context, were 'STOP', but one does not know if this response really can be seen as No Entry or Keep Out, as the message is different in traffic situations, where one may go on after stopping and checking the situation. But with context the STOP sign seems to perform quite well, as responses in the sense of Keep Out reached an almost sufficient percentage.

Recommendation

As test results differ to a large extent between the studies available due to various factors like inconsistent color coding, test settings, scoring deficiencies, etc., we recommend to systematically compare all basic concepts shown in the table below, plus, where reasonable, systematic variations as mandatory and prohibition signs in several real world applications to reach a decisive recommendation.

Tests of pictograms of referent No Entry

Berrio, S., Barrero, L.H., Zambrano, L., & Papadimitriou, E. (2023): Ergonomic factors affecting comprehension levels of traffic signs: A critical review. International Journal of Transportation Science and Technology, Volume 12, Issue 3, 2023, Pages 848-861, ISSN 2046-0430, https://doi.org/10.1016/j.ijtst.2022.08.004

Brugger: Ch. (1996): Verständnistest UIC Kodex Merkblatt 413. Report to ÖBB GD 02 (Austrian Railways), Vienna, March 1996.

Collins, B.L., Lerner, N.D. & Pierman, B.C. (1982): Symbols for Industrial Safety. Washington, D.C.: National Bureau of Standards, NBSIR 82-2485, April 1982.

Easterby, R.S. & Graydon, I.R. (1981 a): Evaluation of Public Information Symbols: ISO Test: 1979/80 Series. Part I: Appropriateness Ranking Tests. AP Report 99, Applied Psychology Department, University of Aston in Birmingham, January 1981.

Easterby, R.S. & Graydon, I.R. (1981 b): Evaluation of Public Information Symbols: ISO 1979/80 Test Series. Part II: Comprehension/Recognition Tests. AP Report 100, Applied Psychology Department, University of Aston in Birmingham, January 1981.

Olgyay, N. (1996): Safety Symbols Art: The Testing Protocol, Materials & Results. Foci Studio, Washington, DC.

Shinar, D., Dewar, R., Summala, H. & Zakowska, L. (2003): Traffic sign symbol comprehension: A cross-cultural study. Ergonomics, 46, 1549-1565.

Silver, N. C., Wogalter, M. S., Brewster, B. M., Glover, B. L., Murray, L. T. A., Tillotson, C. A., & Temple, T. L. (1995): Comprehension and Perceived Quality of Warning Pictorials. Proceedings of the Human Factors and Ergonomics Society Annual Meeting, 39(15), 1057–1061. https://doi.org/10.1177/154193129503901520